Premier League footballer Fabrice Muamba remained in intensive care on Sunday morning after collapsing during an FA Cup tie.
The 23-year-old was said to be critically ill in the London Chest Hospital after falling to the ground at White Hart Lane in front of millions of television viewers watching the sixth round tie between Tottenham Hotspur and his club, Bolton Wanderers.
A joint statement from the club and the hospital at just after eleven o'clock on Sunday morning said the player's condition was unchanged, and thanked the thousands of messages of support from fans around the world.
The statement read:
"Fabrice received prolonged resuscitation at the ground and on route to The London Chest Hospital, where his heart eventually started working.
"As is normal medical practice, Fabrice remains anaesthetised in intensive care and will be for at least 24 hours.
"His condition continues to be closely monitored by the cardiac specialists at the hospital. "
Outside the hospital, the club's manager Owen Coyle said the following 24 hours were "absolutely crucial" and urged people to pray for the player's recovery.
Confusion turned to horror as medics sprinted on to the pitch to begin resuscitating the young man.
Players looked shocked and watched in disbelief as the former England Under 21 star was treated with a defibrillator for several minutes before being stretchered off wearing an oxygen mask and taken to hospital.
World Cup referee Howard Webb abandoned the game.
As the message was relayed around the stadium with the score at 1-1, the fans applauded and chanted Muamba's name.
Premier League chief executive Richard Scudamore said: "The thoughts of the Premier League, its clubs and players are with Fabrice Muamba, his family and Bolton Wanderers.
"We would like to praise the players, match officials, coaching staff and medical teams of both clubs at White Hart Lane for their swift actions in attending Fabrice.
"The league would also like to commend the compassion shown by the fans of Bolton Wanderers and Tottenham Hotspur.
"We hope to hear positive news about Fabrice who is and has been a wonderful ambassador for the English game and the league at Arsenal, Birmingham City and Bolton Wanderers."
Outside the London Chest Hospital, Mr Coyle told Sky News: "Fabrice is critically ill. The next 24 hours are going to be absolutely crucial.
He added: "We've obviously been inundated with people wishing him well and we hope that if everybody can pray strongly tonight that Fabrice is able to recover.
"It's very serious. There's not getting away from that. He's critically ill and God willing he makes it through."
The scene on the pitch recalled memories of Cameroon's Marc Vivien-Foe who collapsed and died during a Confederations Cup match in 2003.
Before the match Muamba took to Twitter to express his excitement over the tie.
Using the username @fmuamba, he tweeted: "Just reach white hart lane. #COYW lets have it now."
Other Premier League footballers posted messages on the website after his collapse.
Wayne Rooney is just one of a host of footballers wishing Muamba well:
Manchester United star Rio Ferdinand wrote: "Come on Fabrice Muamba, praying for you."
England striker Wayne Rooney wrote: "Hope fabrice muamba is ok. Praying for him and his family. Still in shock."
The Football Association (FA) also released a short statement, saying: "Our thoughts and prayers are with Fabrice Muamba and his family right now. A wonderful person."
Former football manager and pundit David Pleat relived the horrific moment when the player collapsed, saying Muamba's arms were seen to "jerk" which he described as "terribly traumatic" and "eerie".
He described Muamba, who played for England all the way through Under 16s to Under 21s, as a good athlete.
He said players were tested rigorously for heart and other problems frequently.
"These things can be genetic and you never know," he told Radio 5 Live.
"The only thing that makes us sit up and think tonight is there are many things more important than football and what's happened tonight is far more important than football."
Muamba was jogging towards his own half when he collapsed.
Bolton manager Owen Coyle ran on to the pitch to check on the status of his player as he received medical treatment, while players gathered and a defibrillator was used on the Zaire-born ex-Arsenal trainee.
Applause greeted the tannoy announcer's revelation the game had been abandoned, and Muamba's name again rang around White Hart Lane.
Ex-Manchester City and West Ham United midfielder Marc Vivien-Foe collapsed and died during a Confederations Cup match in 2003 for Cameroon in Nyon, France.
Motherwell's Phil O'Donnell also fell in a game against Dundee United in December 2007 and passed away.
Tottenham Hotspur's William Gallas reacts on the pitch after Bolton Wanderers' Fabrice Muamba collapses
(left-right) Tottenham Hotspur's Carlo Cudicini, Luka Modric and Louis Saha look concerned after Bolton Wanderers' Fabrice Muamba collapses on the pitch and is resusitated by medical staff
Tottenham Hotspur's Luka Modric (2nd left), Bolton Wanderers' Ivan Klasnic, referee Howard Webb and manager Bolton Wanderers' manager Owen Coyle look on after Fabrice Muamba collapses on the pitch
Tottenham Hotspur's Benoit Assou-Ekotto (left), William Gallas, Carlo Cudicini and manager Bolton Wanderers' manager Owen Coyle look on after Fabrice Muamba collapses on the pitch
Tottenham Hotspur's Jermain Defoe, Ryan Nelsen and Luka Modric react after Bolton Wanderers' Fabrice Muamba is carried off on a stretcher
Tottenham Hotspur's Jermain Defoe reacts on the pitch after Bolton Wanderers Fabrice Muamba collapses on the pitch
Players walk back into the tunnel after the game is abandoned after Bolton Wanderers Fabrice Muamba collapses on the pitch
The medical team tend to Bolton Wanderers' Fabrice Muamba as Ryo Miyaichi, Darren Pratley and Dedryck Boyata look on
Dr Iqbal Malik, a cardiologist at Hammersmith Hospital, told BBC Breakfast that Muamba would have had a cardiac arrest.
He said it was likely to have resulted from an abnormality he was probably born with that had not been picked up "despite the very aggressive screening programme that we do for professional athletes".
Dr Malik said data from London Ambulance Service showed a 25% survival rate once someone had suffered a cardiac arrest and been treated by ambulance crews.
But he added: "I think he's probably in a slightly better situation than that because what he got was immediate attention. The paramedics were there, the physios were there, and he got the defibrillator immediately and had the cardiopulmonary resuscitation (CPR) given to him immediately.
"That meant he's got the best chance of actually having his brain intact as well as having his heart rhythm problems sorted out."
Dr Malik said hospital staff would have to stabilise the heart rhythm, support the blood pressure and cool the body.
He added: "The only thing we can do once we've done all that is to wait and see whether he's going to start making some signs of recovery in the next 24 or 48 hours. The key actually isn't the heart at the moment, it's the brain."
He conceded the situation was like a "timebomb", adding: "What exercise doesn't do is suddenly make it happen when it wasn't going to happen before. Of course it will bring it out, putting a strain on the system is always going to be doing that."
Asked if more can be done in terms of testing, he said: "No, I think the key is the family history and a good physical examination. The biggest risk factor is if there are people in your family who have dropped down dead, you're more likely to have it."