Crystal Palace say manager Roy Hodgson is stable in hospital after he was “taken ill” during training on Thursday morning.
Palace cancelled a news conference after the 76-year-old became unwell.
It was widely reported on Thursday morning that Palace are set to sack Hodgson, with the club 15th in the Premier League and five points clear of the relegation zone.
Palace face Everton at Goodison Park in the Premier League on Monday.
“Following news that Roy Hodgson was taken ill during today’s training session, we can confirm that he is now stable and is currently undergoing tests in hospital,” the club said on X, formerly known as Twitter.
“Everybody at the club sends their best wishes to Roy for a speedy recovery.”
BBC Sport understands that Hodgson is set to lose his job, with former Eintracht Frankfurt boss Oliver Glasner a strong favourite to replace him.
Hodgson took charge of his 200th match as Palace manager earlier this week, with his side beaten 3-1 at Selhurst Park by Chelsea.
The club have won three league games since their victory over Manchester United at Old Trafford in September and have lost 10 of their past 16 top-flight matches.
The former England boss is in his second stint in charge of Palace, having returned for the final 10 games of last season when he signed a short-term deal to take over from Patrick Vieira.
He led the club to 11th in the table before agreeing to continue to manage the side for the 2023-24 campaign.
Supporters have displayed banners in recent weeks calling for Hodgson to be sacked and shared their frustration with how the club is being run.
They voiced their displeasure when he substituted Eberechi Eze after 64 minutes in their FA Cup third-round defeat against Everton last month, with some supporters at Goodison Park chanting “you don’t know what you’re doing”.
Hodgson was also criticised by some Palace fans for sending on Michael Olise as a substitute at half-time against Brighton with the team 3-0 down, despite the winger struggling with injury.
Olise lasted 11 minutes before suffering a recurrence of a hamstring problem.
Glasner, 49, lifted the Europa League with Frankfurt in 2022 during his first season in charge when they beat Scottish side Rangers on penalties in the final.
After guiding Frankfurt to the knockout stages of the Champions League last year, the Austrian left the club at the end of the season with a year still left on his contract, following a 10-match winless run in the Bundesliga.