Manchester United have been made aware of an “alleged incident” involving captain Harry Maguire in Mykonos on Thursday night.
The England defender, 27, is reported to have been arrested following an incident on the Greek island.
Manchester United said in a statement: “The club is aware of an alleged incident involving Harry Maguire in Mykonos last night.
“Contact has been made with Harry, and he is fully co-operating with the Greek authorities.
“At this time we will be making no further comment.”
United players are taking time off after their Europa League exertions earlier this month. The club were eliminated by Spanish side Sevilla last Sunday.