A third Brighton player has been diagnosed with the coronavirus, the club's chief executive Paul Barber has confirmed.
In March the club confirmed that three players had been tested after showing symptoms of the virus and that one had come back positive. Another player later tested positive in April.
The unnamed player will now go into isolation for 14 days.
"It is a concern," Barber told Sky Sports on Sunday.
"Unfortunately we've had a third player test positive yesterday [Saturday], so despite all of the measures that we've been taking over the past few weeks, where the players haven't been involved in any significant training at all, we've still suffered another player testing positive for the virus.
"So there are concerns and I think it's normal for all clubs to have those concerns. We want to make sure we do everything that we can to ensure those protocols are in place and are safe and secure and mitigate the risk as far as we can."
Brighton players will continue to train individually at the club's facilities.
In April the club converted the Amex Stadium into a drive-through testing facility to assist England's National Health Service.
Football in England has been suspended since March 13 with no set date yet as to when it can return.
Clubs are due to meet on Monday to further discuss "Project Restart" which envisages a return to play in June once given the green light from government, with the remaining 92 matches held behind closed doors at neutral venues.
Barber is one of a number of vocal opponents against matches behind held at neutral venues.
Speaking to BBC One's Andrew Marr Show on Sunday Crystal Palace chairman Steve Parish said that it might be a "very, very extended period" before the Premier League returns if they don't find a way to hold matches soon.
"We would be derelict in our duty if we didn't find a way to try and bring the game back," he said.
"The German example could provide a blueprint for us and clearly we can see some of the early challenges.
"They may prove insurmountable, but the concern for us is that if they prove insurmountable now then we may be in for a very, very extended period of not being able to play and that has huge ramifications for the game."
The Bundesliga is due to return on May 16. However, Dynamo Dresden, who play in the second tier, have been forced to quarantine their entire team for 14 days after two new coronavirus cases were detected.
Sources have told ESPN a growing number of Premier League players are not keen to return to football this season and would prefer the league to be cancelled.
Brighton, two points above the relegation zone, have five home games left including visits from Manchester United, Liverpool, Manchester City and Arsenal.
Information from Reuters contributed to this report