The Leicester City owner’s helicopter has crashed in a car park outside the club’s ground shortly after taking off following a match.
Vichai Srivaddhanaprabha was in the helicopter when it came down at about 20:30 BST on Saturday, a source close to the family has told the BBC.
One witness said he saw Leicester player Kasper Schmeichel run out of the stadium towards the scene of the crash.
It is not known how many other people were on board the helicopter.
Leicester City had been playing West Ham United in the Premier League at their King Power stadium.
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.
Vichai Srivaddhanaprabha, from Thailand, purchased Leicester City in 2010
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.”
He said when he ran to the scene “there was a huge fireball” and it looked like the helicopter had crashed in an industrial park next to the stadium.
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.
BBC football commentator Ian Stringer said the helicopter was “spiralling”, and that eyewitnesses said it “came down like a stone”.
He said: “I’ve seen the backroom staff of the first team in tears, the reception area is silent with people just crying.”
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.
One 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.