Speaking to Sky Sports, CEO Paul Barber confirmed a third player has been infected with COVID-19.
"It's worrying. Unfortunately, we had a third positive case of a player, so despite all the measures we've been taking over the last few weeks, the players haven't participated in any group training," Barber said.
"There are concerns and I think it's normal for every club to have those concerns. We want to make sure we do everything we can to ensure that with the protocols it is safe to return and mitigate the risk as much as possible," he added.
Two Brighton players were confirmed positive on 26 March after three members of the England team had shown symptoms of the dangerous disease.
"One of the things we have asked from the Premier League is a complete plan of all the stages to return to play," said a Barber who is against the possibility of playing the remaining Premier League matches in a neutral venue.
"First we need the players to retrain in small groups, then they should engage in some contact training and then train for a match before the League's own offical match," the English team's chief executive officer explained.