The Leicester City owner’s helicopter has crashed in a car park outside the club’s ground shortly after taking off following a match.
It is not known if Vichai Srivaddhanaprabha was in the helicopter at the time.
Leicester City had been playing West Ham United in the Premier League at their King Power stadium.
One witness said he saw Leicester’s goalkeeper Kasper Schmeichel run out towards the crashed helicopter.
Under Mr Srivaddhanaprabha’s ownership, Leicester City won the Premier League in 2016, having started the season as 5,000/1 outsiders.
The game, which ended 1-1, kicked off at 17:30 BST and finished about one hour before the helicopter took off.
One Leicester season ticker holder, who did not wish to be named, said: “I saw 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.”
Freelance photographer Ryan Brown was covering the game and saw the helicopter clear the King Power stadium before it crashed.
He told BBC Radio Leicester: “The engine stopped and I turned round and it made a bit of a whirring noise, like a grinding noise.
“The helicopter just went silent, I turned round and it was just spinning, out of control. And then there was a big bang and then [a] big fireball.”
A Leicestershire Police spokesman said emergency services were dealing with an incident “after an aircraft came down in a car park behind the ground”.
Leicester City said the club was assisting police and emergency services and would issue a more detailed statement in due course.
A spokesman for East Midlands Ambulance Service said they received a call at 20:38 BST to reports of the helicopter crash.
The service has advised members of the public to stay away from the area.
A University Hospitals of Leicester NHS Trust spokesman tweeted to say they were aware of the incident and supporting emergency services.
At the scene
By BBC Sport commentator Ian Stringer
I have seen staff, backroom staff and [the] first team in tears here his evening. The reception area is described as silent, people looking around and crying and not knowing what to do and consoling each other.
I remembering the owners taking over. I said hello to them in native tongue, their face lit up. I have generated relationships with them, seen them in Thailand in Bangkok in their home surrounding, they are really nice people.
The chairman looked at me today on the way to the executive box and said “hello and good afternoon”.
We were keeping a close eye on him because of the nature of today’s game and it is really eerie around Leicester at the minute this evening.
Sky Sports News reporter Rob Dorsett said the helicopter took off from the pitch, as it does after every game.
He said that after a few seconds it appeared to lose control and crashed into the car park just a few hundred metres away.
Another witness said it appeared “the tail propeller wasn’t working, putting it into a spin”.
Leicester mayor Peter Soulsby tweeted that his thoughts and prayers were “with all – particularly owners who’ve done so much for club and our city”.
Labour MP Jon Ashworth, who represents Leicester South, said he had been in touch with emergency services and thanked them for responding so quickly.
Several Leicester City players, including striker Jamie Vardy, and West Ham have tweeted since the crash.
Mr Srivaddhanaprabha bought the club in 2010 for £39m and, after Leicester were promoted from the Championship in 2014, said he would spend £180m to get them into European competition in three years.
Leicester City went on to win the Premier League title in one of the greatest sporting stories of all time following Tottenham’s 2-2 draw at Chelsea in May 2016.
Claudio Ranieri’s side lost just three league games in what was described as a “fairytale” and the “most unlikely triumph in the history of team sport”.
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