The helicopter of Leicester owner Vichai Srivaddhanaprabha crashed outside the King Power Stadium following the Premier League game against West Ham.
The incident occurred in the club's car park, where police cars and emergency services rushed towards an area where flames were visible before the area was evacuated.
Leicestershire Police said: "The aircraft came down in a car park near the stadium shortly after 8.30pm, with Leicestershire Police, East Midlands Ambulance Service and Leicestershire Fire and Rescue Service all responding to the incident."
Srivaddhanaprabha leaves the stadium by his helicopter, which lands in the centre circle on the pitch, after every Leicester home game.
Srivaddhanaprabha, who owns the King Power company, bought Leicester in 2010 and became chairman the following February.
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."
Pete Ripley, associate director of operations at East Midlands Ambulance Service, said: "We received a call at 8.38pm on 27 October to reports of a helicopter crash in the car park of King Power Stadium in Leicester.
"We have sent a doctor in a car, two paramedics in ambulance cars, a crewed ambulance and our Hazardous Area Response Team, with the first resource arriving within two minutes of the call."
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."
Witnesses told Sky Sports News the helicopter took off from the pitch but lost control within a few seconds and crashed into the club's staff car park.
One fan told Sky News the owner and his family have done so much for the club.
He said: "They have conducted themselves so well, they have put everything into us. They have made us champions. You cannot ask for more from your owners."
It is not known who was in the helicopter when it crashed nor what conditions they are in, but there are fears that several people had been killed.
It is also not clear whether anyone on the ground was affected.
Police said the Air Accident Investigation Branch (AAIB) would be leading the inquiry into the circumstances of the crash, adding that a cordon would remain in place while inspectors examined the scene.
Megan Blockley, who was across the road when the crash happened, said: "The damage was really bad. They'd just put the fire out when I got there and it had been burned right through.
"I was just in the bingo hall across the road and I heard the sirens.
"I rushed out and there were four fire engines and loads of police."
One man, who wished not to be named, but has had a season ticket for over 40 years, 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."
Leicester footballers Jamie Vardy and Harry Maguire both tweeted praying hands emojis.
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."
Leicester's Hospitals tweeted: "We are aware of the incident in the vicinity of the King Power Stadium and are supporting emergency services."
Andrew Brodie, Assistant Chief Fire Officer at Leicestershire Fire and Rescue Service, tweeted: "IMPORTANT: Energency Services are dealing with a significant incident @lcfc King Power stadium. It's essential you stay away and allow 999s free movement. More info will follow."
West Ham defender Pablo Zabaleta, who played in the game, tweeted: "My thoughts and prayers are with all those involved in the helicopter accident at Leicester City."
His teammate Declan Rice tweeted: "Horrendous scenes at the king power tonight, my prayers & thoughts go out to everyone involved at Leicester".
