Reports in Greece on Friday morning claimed that Maguire had been arrested while holidaying in Mykonos.
The 27-year-old was enjoying an end-of-season break following United’s elimination from the Europa League at the hands of Sevilla on Sunday.
In a club statement, United said they had made contact with Maguire and would making no further comment.
“The club is aware of an alleged incident involving Harry Maguire in Mykonos last night,” the statement read.
“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.”
Maguire was handed the United captaincy by manager Ole Gunnar Solskjaer in January following the departure of former skipper Ashley Young.
The England international only arrived at Old Trafford in a £80m deal - a world record for a defender - from Leicester City last August.