Watford have launched an investigation into a 20-person gathering reportedly held at striker Andre Gray's home on Friday night.
It is believed team-mate Domingos Quina was among those to have attended the party, which would have been in breach of coronavirus lockdown rules.
And the Premier League club, who are next in action against Southampton on Sunday, are said to be looking into the incident.
According to The Athletic, the club triggered a probe after becoming aware of the reported gathering.