The central England team said it was assisting authorities with "a major incident" at the stadium, after eyewitnesses reported seeing the helicopter plummet to the ground soon after takeoff, about an hour after Leicester's match against West Ham.
While there was no official statement immediately forthcoming about who was on board, or their condition, the BBC reported a source close to the Srivaddhanaprabha family as saying the club's 60-year-old chairman was on the helicopter.
Some seven hours after the crash, police had still made no public statements about casualties.
However, in the early hours of Sunday, Leicestershire Fire and Rescue Service's Assistant Chief Fire Officer Andrew Brodie tweeted that the accident was "clearly serious and tragic", adding "please don't speculate on cause or who may be involved. Think of families, friends, responders, and (Leicester City) and their fans."
Leicester Police said in a statement that its Air Accident Investigation Branch was working alongside the emergency services and the club to "establish the exact circumstances of the collision."
Britain's Daily Telegraph newspaper reported Leicester players and staff, including Denmark goalkeeper Kasper Schmeichel, former Leicester and England goalkeeper Peter Shilton, and distressed club supporters were seen in tears as the helicopter fire raged.
The paper said it took more than 20 minutes for the flames to be extinguished before emergency services were able to survey the wreckage.
Srivaddhanaprabha, who owns Thai duty-free retail giant King Power and is said by Forbes to be the fifth-richest person in Thailand, bought Leicester in 2010 and provided the funds that helped the team improbably win the Premier League at odds of 5,000-1 in 2016.
In a scene regularly seen after matches, Vichai's aircraft arrived in the King Power Stadium after Saturday's 1-1 draw against West Ham before taking off from the center circle. The helicopter usually takes Srivaddhanaprabha back to his English base, in Berkshire, outside London.
Photographer Ryan Brown reported hearing the engine stopping after the helicopter cleared the stadium.
"I turned round and it made a bit of a whirring noise, like a grinding noise," Brown told the BBC. "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."
British broadcaster BT Sport was presenting its post-game show in the stadium when the helicopter took off.
"It suddenly got very serious," BT presenter Jake Humphrey announced later on air. "The helicopter has crashed. It has crashed in the club carpark ... we heard a commotion."
The local ambulance service said it received reports of a helicopter crash at 8:38 p.m. local time and sent a doctor, two paramedics in ambulance cars, a crewed ambulance and its Hazardous Area Response Team.
"The first resource (arrived) within two minutes of the call," the ambulance service said.
An indication of concerns within the Leicester squad came on social media.
The emoji of praying hands was tweeted by several players, including striker Jamie Vardy, whose goals helped the 134-year-old team win the English title for the first time in 2016.
The competition's organizers tweeted: "Thoughts from all at the Premier League are with everyone affected by tonight's incident."