The supporter who collapsed, prompting Newcastle United's Premier League game against Tottenham Hotspur to be halted, is "stable and responsive" in hospital.
Fans in the East Stand at St James' Park alerted players and officials to the incident in the 40th minute.
Tottenham's Sergio Reguilon spoke to the referee and Eric Dier raced to the touchline to urge medical staff to attend with a defibrillator.
Both teams were told to leave the pitch as the game was suspended.
Tottenham were leading 2-1 and had been about to take a corner when Reguilon reacted quickly to a commotion in the crowd and told referee Andre Marriner that a section of fans were calling for assistance.
Players from both teams then signalled the need for medical staff, including Tottenham defender Dier, before the sides left the pitch while the fan received help.
After a delay of more than 20 minutes the rest of the half plus seven minutes of added time were played, with Tottenham scoring a third goal before the delayed interval through Son Heung-min.
Tottenham won the game 3-2.
In a statement, Newcastle confirmed the supporter's condition and added: "The club would like to thank fans for their swift actions in raising the alarm and praise those who provided immediate chest compressions, as well as thanking the on-site medical professionals who swiftly administered emergency treatment using a defibrillator located close to the incident.
"Newcastle United club doctor, Dr Paul Catterson, also attended the incident to offer additional support with an additional defibrillator.
"Our best wishes go to the supporter and their loved ones and we hope for a swift and full recovery."
Reguilon told BBC Sport: "I saw the fans waving and I saw a guy lying down. I saw something wrong had happened. I looked at the gaffer and he stopped the match. I think now everything is OK and 100% happiness.
"It was very strange. We went to the dressing room and I was looking at the man lying down. I was nervous because I don't like to watch that."
Newcastle forward Callum Wilson spoke of the importance of the crowd relaying the message that there was a problem.
"I think it was massive really - the crowd were fantastic and they alerted everyone," he told Sky Sports.
"You could hear fans whistling, shouting, then we saw the space clear where this guy was receiving CPR and then you know how serious it is.
"It was disturbing to see the guy like that. We wish him well and wish him a speedy recovery."
Spurs striker Harry Kane added: "Firstly, we want to say best wishes to the guy in the stands - it was not a good sight to see. We hear that he might be stable now, so we're thankful to the medical teams and the fans who were doing the CPR.
"Hopefully he's OK and we wish him all the best from all the players at Tottenham."
Fabrice Muamba, who collapsed on the pitch at White Hart Lane during Bolton's game against Tottenham in 2012, said: "Once again today shows how important it is to have a defibrillator nearby and how the quick response of people ensures a better chance of survival. I really hope the person makes a speedy recovery."
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