Paramedics desperately tried to resuscitate Premier League footballer Fabrice Muamba but could not get his heart to start beating on its own for almost two hours, it emerged today.
He went into cardiac arrest and paramedics were unable to start his heart working by itself again until he reached London Chest Hospital in Bethnal Green, east London at 8pm.
Muamba remains anaesthetised in intensive care at the hospital which is seven miles away from the stadium.
Today club manager Owen Coyle thanked fans for their support, adding: "All our thoughts and prayers are for Fabrice and his family at this time."
A joint statement from the hospital and Bolton Wanderers read: "Fabrice Muamba remains in a critical condition in intensive care in the Heart Attack Centre at the London Chest Hospital.
"He was admitted to the hospital yesterday evening after collapsing at White Hart Lane where he sustained a cardiac arrest during the FA Cup quarter final against Tottenham Hotspur.
"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."
Coyle added: "Fabrice's family have asked me to pass on their thanks for the many, many kind messages of support from not only Bolton fans but also fans from clubs across the country and abroad.
"All our thoughts and prayers are for Fabrice and his family at this time. The family would also like to thank the media for respecting their privacy at this time."
As a packed White Hart Lane looked on, with a worldwide audience watching live coverage on ESPN, the Trotters midfielder suddenly fell to the floor. 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, accompanied by Coyle and Wanderer's captain Kevin Davies.
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.
Coyle emerged from the hospital in Bethnal Green, east London in the early hours of this morning.
He told reporters: "Fabrice is critically ill. The next 24 hours are going to be absolutely crucial."
Members of his family and his fiancee also attended the hospital last night, it was reported.
This morning fans arrived and left a series of tributes to Muamba outside. Two children left drawings they had made for the midfielder and flowers were left on the doorstep. A Spurs fans who had suffered a similar heart problem delivered a bouquet of flowers.
Coyle and a club medic returned to the hospital this morning.
In a statement Tottenham manager Harry Redknapp said: "All our thoughts are with Fabrice, his family, Owen Coyle and the club.
"It was the right decision to abandon the game. Everybody was in a state of shock and it wouldn't have been right to carry on. Football is the last thing on anyone's mind when an awful situation such as this happens.
"All we are thinking about now is Fabrice and his family."
Club chairman Daniel Levy said: "Our thoughts are with Fabrice's family and Bolton Wanderers and we are all willing him to pull through. Events such as this put everything into perspective.
"We are immensely proud and grateful to the medical teams at both clubs. Their response was immediate and professional.
"Our thanks also to both sets of fans for their support and behaviour. Too often we read the negatives about football and yet last night, at a time of intense emergency and uncertainty, we saw the true humanity and empathy of the footballing family."
Fans left flowers, shirts and scarves at Bolton's Reebok stadium close to the players' entrance and the location of the club's remembrance book.
Supporters arrived throughout the morning to leave tributes.
One message written on a card with a Manchester United emblem on it read: "Our thoughts and prayers are with you. One game, one family."
A Bolton flag was signed with the message: "Just get back to full health. Praying for you."
Two Bolton shirts were left at the scene, signed with messages of support.
An Easter egg was also left by one fan.
A small group of relatives, including Muamba's brother, left the hospital this afternoon but declined to comment.
They were accompanied by a little boy wearing a football strip.
Bolton Wanderers have postponed their next fixture.
The Premier League tie against Aston Villa was due to take place on Tuesday evening, but a statement on the club's statement says that the match has been called off following talks with Aston Villa.
"The club would like to thank Aston Villa and the Premier League for their kind support and understanding at this time," it said.
Dr Steve Cox, director of screening at the charity Cardiac Risk in the Young (CRY), said that sport can significantly increase the risk of a cardiac incident if a person has an underlying condition.
He said: "CRY wants all young people to be aware of the importance of cardiac screening and to have the opportunity to be tested.
"We already provide screening services for a number of professional sporting bodies, including the English Institute of Sport, the RFU, RFL, LTA and a number of FA teams including Manchester City."
He added: "One in every 300 of the young people that CRY tests will be identified with a potentially life-threatening condition.
"Every week in the UK, 12 apparently fit and healthy young people, under the age of 35, die from undiagnosed cardiac conditions. 80% of these deaths will occur with no prior symptoms."
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