The avalanche hit the Castle Peak area of Truckee in California about 10 miles (16km) north of Lake Tahoe, at around 11.30am local time on Tuesday.
The cascade engulfed a group of backcountry skiers, with six people being rescued after they became trapped.
Authorities were still searching for nine missing people on Wednesday morning local time, but have now confirmed eight fatalities and one unaccounted for.
"Eight of the additional nine skiers have been located deceased," Nevada County sheriff Shannan Moon said.
"We are still looking for one of the members at this time."
Ms Moon said the "horrific conditions" and the risk of further avalanches had hampered rescue efforts.
The eight dead skiers were found with their beacons active, and their bodies will be recovered when conditions improve.
One was married to a member of the search-and-rescue team, authorities said.
The group of 15 backcountry skiers - who were outside ski resort boundaries - were returning from a three-day excursion when the avalanche struck, the organising tour company Blackbird Mountain Guides said.
The rescued skiers - including one guide and five clients - had taken refuge in a makeshift shelter made from tarpaulin sheets and communicated with authorities using a radio beacon and text messaging.
The survivors located three others who had died, Ms Moon said.
Two of them were unable to walk because of their injuries and were taken to hospital, she added.
One person had been stabilised and released on Tuesday night, while another person remained in hospital.
The survivors include five women and one man, authorities said.
Rescuers used a snowcat to get within two miles (3.2km) of the survivors, and skied the remaining distance to avoid causing another avalanche.
Ms Moon said the investigators would look into the decision to proceed with the trip despite the weather forecast.
"We're still in conversation with them on the decision factors that they made," she said.
She said it was initially believed that 16 people had been on the tour, but the number was revised to 15 after it was confirmed that one person had pulled out at the last minute.
Avalanche warnings issued
California has been hit by a powerful storm this week, bringing heavy snow, high winds and severe thunderstorms to the mountainous region.
The Sierra Avalanche Center issued an avalanche warning for the area in the Central Sierra Nevada, starting on Tuesday at 5am local time, with large slides expected into Wednesday.
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The rapid accumulation of snow in unstable layers, coupled with gale-force winds had produced the dangerous conditions.
The area near Donner Summit has one of the highest snowfalls in the Western Hemisphere, with an average of nearly 35ft (10m) of snow a year.
The area is named after the infamous Donner Party, a group of pioneers who resorted to cannibalism after becoming trapped in the winter of 1846 to 1847.
The incident marks the deadliest avalanche in the US since 1981, when 11 climbers were killed on Mount Rainier in Washington.
Each winter, between 25 to 30 people die in avalanches in the US, according to the National Avalanche Center.
The 25-year-old left the field during Real Madrid’s Champions League play-off in Lisbon on Tuesday after reporting Benfica winger Gianluca Prestianni to the referee.
But Benfica manager Mourinho appeared apportion some blame to Vinicius, telling reporters afterwards: “A stadium where Vinicius plays, something happens, always.”
On Wednesday, former Manchester United defender Silvestre told Sky News that Mourinho was trying to mislead fans with his comments.
“In terms of what high level and reputation he has, Jose Mourinho failed us," said Silvestre. "As an industry, and as human beings, he completely misled everyone - or he tried.
“But we are not foolish - and we know what happened."
Prestianni, however, has denied making racist comments towards Vinicius, claiming he was "misunderstood" by his opponent.
Mourinho also came under fire for claiming Vinicius had provoked the abuse with his celebration after scoring the only goal early in the second half.
The Brazilian danced around the corner flag, an apparent nod to Cameroonian Roger Milla’s iconic World Cup celebration.
Mourinho told Amazon Prime: "I told him, when you score a goal like that, you just celebrate and walk back."
Silvestre hit back, adding: “For Jose Mourinho to divert and even vilify Vinicius Junior behaviour for celebrating the goal that he did - remembering Roger Milla for Cameroon years ago - it’s not the way a top manager like him should do.
“We expect better, clearly it was bad for everyone, and I hope he's regretting his comment during the game, and also after during the press conference.”
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Silvestre is a member on the FIFA Player’s Voice Panel, tasked with advising on on-pitch racism incidents, alongside legends such as George Weah and Didier Drogba.
Prestianni's response to abuse allegation
In a statement in Portuguese on Instagram, shared by Benfica on social media, Prestianni denied he made any racist comments.
He wrote: “I want to clarify that at no time did I direct racist insults to Vinicius Junior, who regrettably misunderstood what he thought he heard.
“I was never racist with anyone and I regret the threats I received from Real Madrid players.”
Mohammed Algasim, 20, died of a single stab wound across his jugular vein after an altercation on the evening of 1 August last year.
Chas Corrigan, 22, who denies murder and is on trial at Cambridge Crown Court, is seen in CCTV approaching the student and his friends as they sit on a low wall.
Abdullah Bin Shuail, one of Mr Algasim's fellow students, said he heard the pair exchange words but could not make out what they were saying.
Nicholas Hearn, prosecuting, previously told the court the pair had never met before.
Corrigan then walked towards the train station before Mr Algasim said something to him.
Mr Bin Shuail could only make out one word, "centre", Mr Hearn said.
"When Mr Algasim said this, the defendant turned and started to come back towards them," he continued.
The prosecutor said the defendant said "what did you say, what did you say?" in a "very angry and aggressive way".
He said Mr Bin Shuail "saw the defendant punch Mr Algasim hard to the left side of his neck" and "then saw that the defendant was holding a large knife in his right hand".
The stab wound, which also cut across his carotid artery, caused "massive bleeding", Mr Hearn said.
Jane Osborne KC, opening the defence case, said Corrigan "had a kitchen knife - tucked into his waistband rather than in the pocket".
"He will tell you he had no intention of using that knife," she said.
"He had it with him so if he was attacked, as he had been in the past, he could frighten off any attacker.
"He wanted to prevent himself being a victim of violence again."
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She said Corrigan will say "in the incident Mr Algasim was standing in front of him, he thought Mr Algasim was acting aggressively".
"He thought he (Corrigan) was imminently going to be attacked so he produced the knife," she said.
"Having produced the knife Mr Corrigan had no intention of using it to cause Mr Algasim any harm.
"He intended to wave it between them.
"He will say he had no idea he had made contact with Mr Algasim with the knife."
The trial, estimated to last around two weeks, continues.
Bosses said Heraeus Medical, its supplier, had suffered a packaging fault involving its bone cement products.
The health service, which is seeking alternative suppliers, said the issue had halted production at Heraeus' main site for at least two months.
It estimates it has two weeks' worth of supplies left, therefore leaving a supply gap of six to eight weeks, and urged trusts to review and prioritise waiting lists to maximise use of available stock.
The products are used for joint surgery, including hip and knee operations. Each year, tens of thousands of patients in England are given hip or knee replacements.
President of the British Orthopaedic Association, Fergal Monsell, said it would update surgeons as the situation developed.
Alternative supplies
Responding to reports operations could be cancelled, he said: "The BOA is working with NHS Supply Chain, NHS England and the relevant Specialist Orthopaedic Societies to identify possible alternative supplies and evidence-based practice to reduce the impact on patients.
"This is a situation that is beyond the control of trauma and orthopaedic surgeons and NHS organisations.
"The solutions we are recommending are designed to lessen the impact on patients and will be determined on the basis of safety and identified clinical need.
"NHS trusts have also been advised to utilise the released theatre time to treat orthopaedic patients where procedures do not require the use of cement.
"The BOA will update surgeons with developments so they can treat their patients as the situation develops."
'Any stock already in hospitals is unaffected'
An NHS spokesperson said existing stock would be unaffected.
They said: "Following a global supply issue, the NHS is issuing immediate guidance to hospitals to ensure trauma and urgent care can safely continue, enable the use of alternative suppliers where possible, and to support prioritisation of orthopaedic waiting lists based on patients' needs over the coming weeks.
"Any stock already in hospitals is unaffected, and the NHS is working closely with government and leading professional bodies to ensure safe and effective care can be provided while supply is resolved, and to reduce delays for patients requiring less urgent care as far as possible."
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Deborah Alsina, chief executive of Arthritis UK, said the news was a "crushing blow" to patients who were expecting surgery after "a long time waiting".
She added: "We trust the Department of Health and Social Care will work hard to address the supply issues given the impact on those waiting in pain whose lives are left on hold.
"Aside from the personal toll on people with arthritis, the stakes are high for government who have an uphill challenge to bring down waiting lists to meet ambitious targets."
Warning: This story contains descriptions some readers may find distressing, including references to suicide.
Kerri-Anne Donaldson's body was discovered in Farnborough, Hampshire, on 7 June 2023 - the day after she was discharged from hospital.
The 38-year-old had been taken into custody and questioned at a police station on suspicion of "child sex offending" three days before her death, the hearing was told.
Ms Donaldson, who reached the semi-final of the TV talent show in 2014 as part of dance group Kings and Queens, was arrested on 4 June 2023 about the alleged sex offence, which she denied.
After going missing and being found at a hotel in Woking, Surrey, she was taken to nearby St Peter's Hospital, having taken an overdose.
But she was discharged on 6 June, then Ms Donaldson was found dead at her home the following morning, Winchester coroner's court heard.
At an inquest into her death, the coroner heard Ms Donaldson told the alleged victim she would take her own life "if someone finds out" about the allegation made to police.
Detective Constable Benjamin Harris, of Hampshire Constabulary, said he considered the possibility Ms Donaldson's reported comments could be a "form of control" against her accuser.
He said: "In my experience in some offences it can often be said without wanting to carry it out."
After being taken to hospital following her arrest and deemed a "high and imminent risk of suicide", she was later ruled suitable for release as she had "settled", allowing her to be discharged.
Consultant psychiatrist Dr Martin Williams, who was one of three mental health workers who carried out an assessment of Ms Donaldson before her release, told the inquest she was suffering from an "acute adjustment reaction" to her arrest.
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A psychiatric nurse rated her risk at level 10 out of 10 on 5 June, but the next day she was assessed as having changed her position from the previous evening and was released.
Dr Williams said: "I was able to form a snapshot of the risk she was posing at that point, she expressed clearly that she didn't have plans to carry out acts that could lead to her death.
"It struck me how warm and personable Kerri-Anne was, it struck me she was open, she was receptive, she was showing emotions appropriate of what she was facing."
Dr Williams added: "We considered the possibility she was masking a higher level of risk than she was saying, but all the indications were that she was settling and the risk was markedly reduced from the previous day."
Dr Williams said hospital staff were told the nature of the allegation by either police or Ms Donaldson, but she told him she no longer believed she was "definitely going to go to prison".
He said: "She had shifted from a position of quite stressed and downbeat about the police involvement to where she felt much more confident."
Dr Williams said Ms Donaldson said she "wanted to take her own legal advice and wanted to fight the case".
He added: "She believed she had a good case in putting together a defence to whatever the arrest was for, she believed she had a good case.
"She expressed a view on the day of the assessment, she was no longer so worried about going to prison."
Detective Chief Superintendent Sarah McConnell, of Hampshire Constabulary, said the officer who carried out an enhanced risk assessment of Ms Donaldson while she was in hospital acted "appropriately" by not revealing to the medical team what she had been arrested for.
No further details about the nature of the allegation, other than it was over "child sex offending," were heard during the inquest.
The hearing continues.
Anyone feeling emotionally distressed or suicidal can call Samaritans for help on 116 123 or email jo@samaritans.org in the UK. In the US, call the Samaritans branch in your area or 1 (800) 273-TALK