The NRL integrity unit is aware of an alleged incident involving Dylan Walker and Aaron Gray while on holiday in Thailand.
According to reports a man whose son was arrested on the island of Phuket, complained to the integrity unit of the behaviour of Manly utility Walker and South Sydney outside back Gray.
The Rabbitohs and the Sea Eagles are also looking into the alleged incident.
Walker and Gray made headlines as the end of last season when they were admitted to hospital after overdosing on prescription drugs.
Walker moved to Manly from Souths ahead of the 2016 season.
The NSW representative was also fined $10,000 by Manly earlier this year after he injured his hand while attempting to get into his apartment.
Walker missed three weeks due to the injury.