The Learjet aircraft erupted into a massive fireball in a residential area near Cresthaven at around 12.50pm local time (5.50pm UK time) on Sunday.
Transportation secretary Sean Duffy confirmed all nine on board had died, calling it a "horrific tragedy".
He said: "Please join me in praying for the families and loved ones of those we lost."
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The plane had departed Austin-Bergstrom International Airport in Texas and was heading to North Eleuthera Airport in the Bahamas.
Florida governor Ron DeSantis said there were no immediate reports of anyone on the ground injured or killed.
The circumstances of the crash remain under investigation.
"It was a cataclysmic plane crash," Mr DeSantis told reporters at the scene. "It looked like a missile going down and left a big crater on the side of the road."
He said there was a lot of debris scattered over a "significant distance".
Images also showed damage to a section of the road and flames on the ground.
In footage of the crash, the aircraft can be seen nose-diving and erupting into a giant fireball near a major roadway just inches from passing vehicles, appearing to narrowly miss homes.
The plane was making its way east at 35,000ft when pilots reported turbulence, icing and precipitation and requested to climb another 2,000ft.
Moments later, the jet entered a steep dive, speeding it beyond its design limits, according to air traffic control recordings and flight tracking data.
"We're descending 8,000 - mayday, mayday - we're descending 10,000ft per minute," the pilot radioed.
"We're going to crash into the ground."
About 35 seconds after the initial mayday announcement, the last thing heard from the cockpit was "we're out of time".
Jim Reynolds, a spokesperson for Austin-Bergstrom International Airport, said the jet was a private plane, but could not immediately provide details about who was on the flight.
Rain pounded the region on Sunday and a flood watch was in effect through Monday afternoon, the National Weather Service said.
A woman working nearby said electricity in the area had been out for around two hours following the crash.
Palm Beach County authorities were evacuating around 600 people from a nearby mobile home community while federal officials investigate the incident. The road will be shut until further notice, county officials said.
The Federal Aviation Administration is sending a team to support the National Transportation Safety Board's investigation, Mr Duffy said.
The two-time Olympian, who won the European title in Rome in 2024, from Portaferry, Co Down passed at 6.30am on Sunday.
Mageean announced last year that she had been diagnosed with cancer.
Her family said in a social media post that she was surrounded by her loved ones.
They said: "A beloved daughter, sister, wife, friend and inspiration to so many, she will be deeply missed."
Mageean represented Ireland at the 2016 and 2020 Olympics, in addition to holding a number of Irish records.
She became the first individual Irish European champion since Sonia O'Sullivan when she struck gold at the 2024 championships in Rome but was unable to compete in the 2024 Olympics due to an Achilles injury.
Mageean announced her diagnosis of stage 4 bowel cancer the following year.
She went on to marry her partner Thomas Moran in October just weeks before her death.
Taoiseach Micheal Martin said he was deeply saddened by the news.
"My heartfelt sympathies go to her husband Thomas, all her family and friends," he said in a statement on the social media network X.
Tanaiste Simon Harris described the news as heartbreaking.
He said on X: "She was a European champion, two-time Olympian, a proud Irish athlete and an extraordinary person."
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Northern Ireland's First Minister Michelle O'Neill said Mageean demonstrated "extraordinary talent, determination and dedication".
"From representing Ireland at two Olympic Games to winning European Championship gold in Rome in 2024, Ciara demonstrated extraordinary talent, determination and dedication," she said.
"However, beyond the medals, records and sporting accolades, Ciara will be remembered for her warmth, courage and tremendous strength of character.
"Throughout her illness, she showed a remarkable spirit and an incredible ability to find hope and joy in life, even in the most difficult circumstances. Her courage touched countless people and will leave a lasting legacy.
"For a community like Portaferry, this loss will be deeply felt. Ciara was one of our own, and the pride she brought to her community and beyond will never be forgotten."
A statement from Athletics Ireland read: "Ciara was a much-loved and inspirational figure who touched the lives of so many. Her courage, warmth and spirit will leave a lasting legacy."
The "anti-migrant" group had been travelling on a minibus which they nicknamed "the battle bus" and were in possession of four tear gas bombs, said officials in the Hauts-de-France region.
The five, who were apprehended in Grande-Synthe, about four miles from Dunkirk, had been broadcasting live on social media, "images intended to illustrate acts of intimidation" against migrants trying to reach the UK, it was alleged.
Authorities said the suspects were placed in police custody and have been accused of participating in a "group formed with a view to preparing violence against persons and for transporting category D weapons without legitimate reason".
The Dunkirk prosecutor's office is involved in the investigation and the five are expected to be "expelled" from France.
Officials in the Hauts-de-France region said 10 other suspected far-right activists from Britain, who were detained under similar circumstances earlier this year, have been slapped with bans from French territory.
"The state does not tolerate such actions conducive to hatred and violence from anyone," said the X account of the Prefecture de la region Hauts-de-France et du Nord.
It is the official government administrative body which represents the state in the Hauts-de-France region and the Nord department.
On Saturday, the UK government announced almost 1,000 migrants crossed the English Channel in small boats to the UK in two days, as better weather led to calmer conditions.
Officials said 263 people in three boats made the journey on Thursday, which ended a three-week pause in crossings from France.
That was the longest spell without arrivals this year amid high sea swell and wind in the Channel.
Then on Friday, 671 people in nine boats made the journey to Britain.
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With crossings usually lower during late autumn and winter, data suggests the total number of crossings this year is unlikely to surpass the figure for 2025.
According to the Home Office, the total number of arrivals for 2026 was 21,869 after Friday's crossings. The figure for the whole of 2025 was 41,472.
Crossings are down significantly, with the lowest number of summer arrivals since 2020 recorded this year, the government said.
In April, Home Secretary Shabana Mahmood signed a three-year £662m deal which was expected to see French police removing hundreds of migrants from beaches every year.
Riot police would be sent to stop migrants entering the Channel as part of measures which came into force in the summer, typically the busiest time for crossings.
Sky News has learnt that National Grid Electricity Transmission last week signed a deal to purchase more than 70 acres of land at Dorman Point on a site owned by Teesworks, a local private-public partnership.
Sources said the power infrastructure group had drawn up plans to construct a large substation which would provide power to a vast neighbouring data centre, which sources said was likely to be the largest in Europe.
The site is understood to have drawn significant interest from US-based frontier labs and technology hyperscalers in recent months.
One tech industry source said competition for the Teesside location was likely to lead to an investment decision with a preferred partner in the coming months.
"Sovereign AI in the UK requires UK-based infrastructure," said an industry source.
"Despite numerous announcements and smaller sites elsewhere in the UK, it's clear that the data centre project in Teesside is the only real opportunity for UK plc to deliver its hopes of true sovereign AI."
The National Grid deal with Teesworks underlines the importance of resolving power supply bottlenecks, with grid connection delays having become one of the single-biggest blockages to industrial development in Britain in recent years.
It also comes at a time when mounting concerns over UK data sovereignty - particularly in areas of sensitive public services and national security - have spurred demands to reduce reliance on overseas tech giants.
"Securing this land agreement is an important step forward in the development of the new substation," Matt Pearce, National Grid head of lands, said in a statement this weekend.
"It reflects the constructive work between all those involved to enable this vital infrastructure which is part of The Great Grid Upgrade, the largest upgrade of the electricity grid in generations, and will support the growth of AI and digital technologies and enable the region's next phase of industrial and economic development.
"We are committed to working closely with our partners to progress the development as quickly as possible."
In documents published alongside last week's budget, the government unveiled a national policy statement on data centres in which it described them as "as fundamental to our economy as the railways and electricity networks on which we have long depended".
"We must take control over the development of data centres in this country and ensure that the country and host communities benefit from them," it said.
"We therefore must be clear about what we expect in return: infrastructure that strengthens our national sovereignty, protects billpayers, delivers real benefits for local communities and helps reindustrialise Britain."
The explosion in the data centre industry has also fuelled a backlash in some communities, with complaints about pressure on local power and water supplies spurring an intense debate about their desirability.
In a statement issued to Sky News, Ben Houchen, the Tees Valley Combined Authority mayor, said: "Everyone who has tried to build a data centre in this country knows the biggest problem is getting enough power to the site quickly.
"While we've been stuck in the queue, the US, the Gulf and parts of Europe have been getting on with it and hoovering up the investment.
"Having up to 3.2GW of capacity here means we can finally compete for those projects.
"If Britain is serious about having its own AI capability, with sensitive data stored safely on British soil, it needs somewhere to physically put it, and I'd much rather that was Teesside than Texas or Abu Dhabi.
"Full credit to Steel River Power, Iberdrola and Teesworks for getting it over the line, and I have no doubt it'll mean thousands of good jobs for local people over the next few years."
Sources said that Balfour Beatty, the London-listed infrastructure services group, was in line to deliver the Teesworks substation for National Grid, with Steel River Power (SRP), which owns and operates the private electricity network across the estate, also heavily involved in the project.
SRP is a joint venture between Steel River Energy Limited and North West Electricity Networks, part of the energy giant Iberdrola, which owns the UK supplier ScottishPower.
Teesworks encompasses 2,500 acres, making it Europe's biggest brownfield site, and its ownership has drawn scrutiny over the profits made by its owners.
The entity is structured as a private-public partnership, with 10% owned by the public sector South Tees Development Corporation.
"Making this land available for what is expected to be the UK's largest substation is an important step in putting the infrastructure in place to support the next phase of industrial development across the site," Chris Musgrave, the Teesworks chairman, said.
"Our focus now is on delivering the remediation works and preparing the land for handover, helping to ensure Teesworks is ready to support the energy needs of major businesses and industries for years to come."