Muamba fell face-down to the field near the midfield line without any players near him.
Medics rushed onto the field with a defibrillator and treated the 23-year-old, pumping his chest for around six minutes of treatment before he was rushed to hospital.
Bolton Manager Owen Coyle and striker Kevin Davies accompanied Muamba to hospital and Coyle later gave an update to Sky News saying, “Fabrice is critically ill. The next 24 hours are going to be absolutely crucial.”
“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,” Coyle said. “It’s very serious. There’s not getting away from that. He’s critically ill and God willing he makes it through.”
Earlier, Bolton had released a club statement which said: “Fabrice Muamba has been admitted to the heart attack center at London Chest Hospital where he is currently in a critically ill condition in intensive care.”
Tottenham players William Gallas and Louis Saha along with referee Howard Webb immediately called for medical support as the game was stopped and live television coverage turned away from Muamba.
Muamba was carried off on a stretcher with an oxygen mask and with his chest still being pumped as the crowd applauded. All the players also left the field before Webb abandoned the match.
Former Arsenal teammate Johan Djourou wrote on Twitter that he had visited Muamba on Saturday night.
“Just left the hospital,” he said. “Love you so much man! Keep fighting. Everybody please pray for him he’s an amazing man and friend.”
Tottenham striker Jermain Defoe, who played in Saturday’s match, tweeted: “God willing he will pull through.”
Muamba’s Bolton teammate Stuart Holden, who was watching the game on television, tweeted: “Praying for you Fab.”