With 41 minutes of the game gone, with no one near him, 23-year-old Muamba suddenly collapsed to the floor and lay with his face down on the turf at the north London ground.
He is said to be "critically ill" in intensive care at the heart attack centre of the London Chest Hospital, the club have confirmed.
Muamba collapsed in the 41st minute of Bolton's FA Cup quarter-final against Tottenham tonight, with the match abandoned after the player received treatment on the pitch from paramedics.
He was rushed to hospital and the club have now released a statement which reads: "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.
"No further information will be issued at this stage. The club has requested the media to respect his family's privacy at this time."
The England Under-21 star underwent six minutes of treatment amid worrying scenes at the north London ground.
He was wearing an oxygen mask and was then rushed to the London Chest Hospital in Bethnal Green in east London.
Fans are anxiously waiting to hear more about the condition of the player, who collapsed when the game was tied at 1-1.
Within a second of seeing Muamba fall to the ground, Bolton manager Owen Coyle shouted "he's just collapsed" before running on to the pitch to be alongside his player amid a sombre atmosphere at Tottenham's ground.
Both sets of fans chanted the player's name as he was being treated and Tottenham forward Rafael van der Vaart and Muamba's team-mate Tuncay Sanli both prayed for the former Arsenal player on the pitch. Some fans cried at the sight of seeing a player out cold on the pitch.
Muamba was carried off on a stretcher while wearing an oxygen mask and referee Howard Webb abandoned the match moments later.
It is understood Coyle and Bolton's veteran striker Kevin Davies accompanied Muamba to the hospital. Worried fans and players took to Twitter to give their reaction to Muamba's collapse.
Middlesbrough defender Justin Hoyte, who came through the Arsenal youth team with Muamba, posted: "I seriously hope my best friend in football is OK. Stay strong bro please please stay strong.
"God is with you remember that."
Muamba's Bolton team-mate Stuart Holden wrote: "Praying for you Fab. Hope he's OK. Thoughts with him and his family.''
Spurs striker Jermain Defoe said: "Pray for fab god willing he will pull through #PrayForMuamba."
Muamba started his career at Arsenal and spent two years at Birmingham before joining Bolton in 2008.
He was born in Zaire, now known as the Democratic Republic of Congo, but has represented England from under-16 to under-21 level.
Spurs fan Paul Smith was at the game. He told of his horror at seeing the sad events unfold.
He said: "I, along with around 30,000 other people have witnessed a great tragedy this evening.
"Bearing in mind that the lad was given resuscitation on the pitch, we fear the worst.
"It puts everything else into perspective and the thoughts of all Spurs fans are with him and his family.
"I was in the north upper stand and the incident was in the other half of the field so I was quite a long way from everyone but everyone saw the urgency of the situation.
"He was just laying face down on the pitch."
Football Association chairman David Bernstein said: "On behalf of The FA, I would like to send our thoughts and prayers to Fabrice Muamba and his family this evening.
"Fabrice has played 33 times for England Under-21s, captaining Stuart Pearce's side during this time and is a player, and more importantly, a person we care greatly for.
"We are in contact with Bolton Wanderers over Fabrice's condition and are awaiting updates."
Bolton had taken the lead during the match when Darren Pratley's header flew in off Gareth Bale's shoulder.
Tottenham equalised five minutes later when Kyle Walker powered home a Bale cross at the back post after 11 minutes.
Half an hour later Muamba collapsed and the game was abandoned.
Premier League chief executive Richard Scudamore sent his organisation's best wishes to Muamba and his family.
He 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."