A helicopter used by Leicester City Football Club owner Vichai Srivaddhanaprabha crashed in flames near the club's stadium, leading to fears there would be no survivors.
Witnesses said the helicopter seemed to spiral out of control moments after it set off from Leicester's King Power Stadium at about 8.30pm on Saturday and plummeted into the car park.
Mr Srivaddhanaprabha is known for arriving and leaving the stadium in his helicopter at home games.
But it is not known whether he was in the aircraft, believed to be his Agusta AW169 helicopter, when it crashed.
Videos posted on social media show emergency services personnel rushing towards the wreckage, which was engulfed in flames shortly after the Premier League game against West Ham.
The footage, taken by Sky Sports News, shows members of the emergency services approaching a cordon around the inferno.
A police spokeswoman said: "Emergency services are currently dealing with an incident at the King Power Stadium, in Leicester, after an aircraft came down in a car park behind the ground earlier this evening.
"Officers are working alongside the ambulance service, Leicester Fire and Rescue Service, the Air Accident Investigation Branch and Leicester City Football Club to establish the exact circumstances of the collision."
We are dealing with an incident in the vicinity of the King Power Stadium. Emergency services are aware and dealing.
— LeicestershirePolice (@leicspolice) October 27, 2018
East Midlands Ambulance Service said the alarm was raised at 8.38pm and it sent a doctor, ambulance and team of paramedics alongside a hazardous area response team to the car park outside the stadium.
It has not been confirmed how many people were in the helicopter or how serious their injuries are, and it is not clear whether anyone on the ground was affected.
But there are fears that the crash and resulting fireball could have left the pilot and passengers little chance of survival.
One witness told Sky News: "I hope they're okay. Doesn't seem like they have had much of a chance. Just burst into flames."
Witnesses told Sky Sports News the helicopter took off from the pitch but lost control within a few seconds and crashed in the club's staff car park.
The website Planefinder said that Mr Srivaddhanaprabha's Agusta Westland AW169 helicopter set off from near Fairoaks Airport in Surrey at about 2.45pm on Saturday, and travelled into Fulham, west London, before turning north and proceeding to the King Power Stadium in Leicester.
Mr Srivaddhanaprabha, who owns the King Power company, bought Leicester in 2010 and became chairman the following February, leading the club as they became Premier League champions in 2015-16.
Leicester City footballers Jamie Vardy and Harry Maguire both tweeted praying hands emojis.
A Leicester City spokesman said: "We are assisting Leicestershire Police and the Emergency Services in dealing with a major incident at King Power Stadium. The Club will issue a more detailed statement once further information has been established."
Jonathan Ashworth, Labour MP for Leicester South, tweeted: "Awful horrific scenes at @LCFC with the helicopter crash. I've been in touch with our emergency services and thanked them for responding so quickly. Our hopes and prayers for all those caught up in this desperately awful incident."
One man, who wished not to be named, but has had a season ticket for over 40 years, said: "I saw (Leicester goalkeeper) Kasper Schmeichel run out first and then loads of security guards and stewards.
"I was stood outside the ground but it crashed on the other side.
"I hope everyone is OK."
Amir Mahmoud, St John Ambulance district manager for Leicestershire, Northamptonshire and Rutland, tweeted that all their volunteers were safe, adding: "My thoughts are with those involved in the tragic incident that has happened tonight."