In a series of social media posts, including images and voice notes, the 20-year-old has been accused of domestic violence by his girlfriend.
Man United have said that they are "aware of images and allegations" relating to the youngster but will not be making "any further comment until the facts have been established".
"We are aware of images and allegations circulating on social media," read a statement from the club. "We will not make any further comment until the facts have been established. Manchester United does not condone violence of any kind."
Greenwood has made 129 appearances for the Red Devils since breaking into the first team, netting 35 times and contributing 12 assists in the process.
The England international's last appearance for Ralf Rangnick's side came against West Ham United on January 22, playing 82 minutes of his team's 1-0 success at Old Trafford. body check tags ::