The episode could be a career-ending one for the playmaker after previous off-field incidents.
In the video an intoxicated Pearce urinates on himself and makes an advance at a woman, before being kicked out of the party.
The Roosters have said they are “aware of an incident involving Mitchell Pearce”.
“The Club will conduct an internal investigation and will be making no further comment at this time,” it said in a statement.
The NRL has asked the Roosters for a report into the incident.
“The Integrity Unit will work with the Roosters to ensure the matter is dealt with appropriately,” an NRL spokesperson said.
Pearce, who made his debut for the Roosters in 2007, has made more than 200 appearances in the NRL.
More to come.