The Leicester City owner’s helicopter has crashed in a car park outside the club’s ground as it left the stadium following a Premier League 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 had drawn 1-1 against West Ham United at the King Power Stadium.
The game kicked off at 17:30 and finished about one hour before the helicopter took off.
Under Mr Srivaddhanaprabha’s ownership, Leicester City won the Premier League in 2016, having started the season as 5,000/1 outsiders
One Leicester season ticker holder, who did not wish to be named, said: “I saw Kasper Schmeichel run out first [from the stadium] and then loads of security guards and stewards.
“I was stood outside the ground but it crashed on the other side.”
Another witness said it appeared “the tail propeller wasn’t working, putting it into a spin”.
In the early hours of Sunday, Leicestershire Fire and Rescue Service’s Assistant Chief Fire Officer Andrew Brodie tweeted that he had just left “multiagency strategic meetings” at Leicestershire Police’s HQ.
He described the crash as “clearly serious and tragic”, adding: “Please don’t speculate on cause or who may be involved. Think of families, friends, responders, and @LCFC and their fans.”
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.”
Leo Bruka told 5 Live that he saw two police officers whose car was near the crash scene.
“One of them was looking for something and the other one, he ran straight away to the helicopter and he was trying to break the window,” he said.
“Then there is an explosion and they pulled back because the fire was too hot.”
Leicestershire Police said officers were working alongside the other emergency services, the Air Accidents Investigation Branch (AAIB) and Leicester City FC to establish the circumstances of the collision.
In the early hours of Sunday the force tweeted that the AAIB, which said it had sent a team to the stadium, was leading the investigation.
Leicester City said the club was assisting police and emergency services and would issue a more detailed statement in due course.