Bolton have announced that Fabrice Muamba is 'in a critically ill condition in intensive care' after collapsing at White Hart Lane on Saturday.
The 23-year-old collapsed to the turf during the Trotters' FA Cup quarter-final contest with Tottenham.
Medical staff spent 10 minutes tending to Muamba on the field as they attempted to resuscitate him.
He was stretchered off and rushed to hospital, with the game abandoned after 41 minutes.
Muamba, a former England U21 international, was taken to the London Chest Hospital in Bethnal Green - just nine miles from White Hart Lane.
Players, coaching staff, match officials and supporters were visibly shaken by the events, with concern expressed from all corners of the sporting community.
Bolton have confirmed that Muamba suffered a heart attack on the field of play and is currently being cared for by specialists.
"Bolton Wanderers can confirm that Fabrice Muamba has been admitted to the heart attack centre at London Chest hospital where he is currently in a critically ill condition in intensive care," read a statement on the club's official website.
"No further information will be issued at this stage. The club has requested the media to respect his family's privacy at this time."