The 21-year-old was reported to have held a rowdy late-night party at a Birmingham hotel following his side’s 0-0 draw with Ipswich Town on Saturday.
According to the Daily Mail, balloons containing nitrous oxide, known as hippy crack, were found in the room and police were called to halt the bash.
It is not the first time Grealish’s off-field behaviour has been called into question.
The youngster was forced to apologise to then-Villa boss Tim Sherwood early in 2015 after pictures emerged of him inhaling from balloons.
He was subsequently pictured that summer drunk and sprawled out on a road while on holiday in Tenerife.
Grealish, who has made eight appearances for the Championship side this season, could be facing a fine of two weeks’ wages – around £50,000 – for his latest indiscretion.