The 27-year-old, who is the world’s most expensive defender following his £80million move from Leicester to Old Trafford last summer, was one of three Englishmen arrested by Greek police on Thursday night.
The head of the press office for the Hellenic Police’s South Aegean region said there had been an altercation and an exchange of words with the police, and that the three men would appear before a prosecutor on the island of Syros later on Friday.
United said: “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. The Europa League final will take place in Germany on Friday night.
In his first season at Old Trafford Maguire was an ever-present in the Premier League, scoring one goal.
Maguire’s representatives have been contacted for a response.
The player was one of the Premier League captains who drew praise for his involvement in the #PlayersTogether initiative, which helped raise funds for the NHS during the coronavirus pandemic.
