American football star Damar Hamlin is in a critical condition after collapsing during a primetime US National Football League game.
The Buffalo Bills player, 24, fell to the ground after colliding with an opponent during the first quarter of a match against the Cincinnati Bengals.
He received on-field medical attention for over 30 minutes before being taken to a local hospital, AFP reported.
The NFL suspended the game for the night about an hour after the incident.
Jordon Rooney, Hamlin's representative, wrote on Twitter: "His vitals are back to normal and they have put him to sleep to put a breathing tube down his throat. They are currently running tests. We will provide updates as we have them."
Hamlin, who plays in the role of safety, was tackling the Bengals' receiver Tee Higgins when Higgins' helmet appeared to hit Hamlin in the chest. After initially getting to his feet, he fell on his back.
Medical officials administered CPR to Hamlin on the field for more than 10 minutes and provided him with oxygen as he left on a stretcher, ESPN said.
The outlet also reported that members of Hamlin's family, who were attending the game, rode with him in the ambulance to the nearby hospital.
Players from both teams gathered around Hamlin during the treatment. Several were seen visibly distressed, with many kneeling to pray and some in tears.
Television coverage repeatedly broke away from the scene on the field, and the crowd in Cincinnati remained silent during the ordeal.
Organisers reached the decision to officially suspend the game for the night about an hour after the incident. NFL games are rarely suspended because of injury.
Joe Danneman, a local sports reporter, said a source had informed him the Bills would fly back home to New York rather than stay in Cincinnati. It means the game may not resume anytime soon.
The two teams are among the top Super Bowl contenders this year, with their head-to-head coming in the primetime Monday night slot in the penultimate week of the NFL's regular season.
The league's players association wrote in a statement: "We have been in touch with Bills and Bengals players, and with the NFL. The only thing that matters at this moment is Damar's health and well being."
Hamlin, a native of McKees Rock, Pennsylvania, was a standout at the University of Pittsburgh before being drafted by the Bills in the 2021 NFL draft.
Playing in the role of safety, he served as a reserve for much of last year but has been a part the Bills' starting line-up in 2022.
He has also drawn praise for hosting annual Christmas toy drives in his hometown since before he was a paid athlete.
An online GoFundMe page for the toy drive was reshared after Hamlin collapsed on Monday and has raised nearly $1m.
Well wishes have also poured in from many corners. Arizona Cardinals defensive end JJ Watt wrote on Twitter: "Please be ok man. Please be ok", while retired Pittsburgh Steelers safety Ryan Clark told ESPN's SportsCenter show: "This isn't about a football player, this is about a human."
New York Governor Kathy Hochul said: "Praying for Damar Hamlin. Our hearts are with his family, loved ones and the entire Buffalo Bills community."