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.
The game, which ended 1-1, kicked off at 17:30 BST and finished about one hour before the helicopter took off.
Mr Srivaddhanaprabha was at the game and spoke to BBC commentator Ian Stringer on his way to the executive box before the match.
Under Mr Srivaddhanaprabha’s ownership, Leicester City won the Premier League in 2016, having started the season as 5,000/1 outsiders.
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.”
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. I hope everyone is OK.”