Watford omitted Andre Gray, Nathaniel Chalobah and Domingos Quina from their squad for the Premier League game against Southampton on Sunday as a precautionary measure, the club said in a statement.
Media reported that striker Gray had breached coronavirus lockdown rules by holding a birthday party at his home this week, with Quina also pictured at the gathering.
"Gray, Chalobah and Quina have all been omitted from the Watford squad by (manager) Nigel Pearson to ensure the health and safety of all players, staff and officials at today's game," Watford said.
The club said on Saturday they were investigating the matter and would speak to the players involved.
