A Montreal police officer is being treated for severe head injuries in a Quebec hospital after he was violently attacked while on vacation in Mexico.

The off-duty assault occurred last Saturday at a nightclub in the popular resort city of Cancun while the officer was on a week-long vacation in nearby Playa del Carmen with seven fellow police officers.

Few details are known about the nature of the assault or the other person or people who were involved because the officer in question is unconscious in a Montreal hospital and hasn't been able to speak to investigators.

CTV News has learned the injured man was at the bar with two other officers, but he became separated from them and wasn't at the hotel when they returned after 3 a.m.

Out of concern, the pair returned to the bar and found the badly injured man, who has been a police officer for four years.

Suffering from serious head injuries, the officer underwent surgery in a Mexican hospital and was airlifted to Montreal on Thursday to receive further care in a facility that's closer to home, Montreal police spokesman Ian Lafreniere told CTV.

Even though the assault occurred in a different country, investigators with the Montreal Police Service are probing the matter. Police are looking into the possibility that the officer was assaulted during a run-in with at least one Canadian member of an outlaw motorcycle gang who recognized the officer in the bar.

Police in Montreal have spoken to their counterparts in Mexico, who say the officer was injured during a bar fight with a fellow tourist.

"So, that's the first possibility. It's still barely possible," Lafreniere said. "On the other side, was he targeted (for) being a police officer?"

Police are leaning towards the scenario that the man was targeted. Officers are waiting for a possible suspect to return to Canada from Mexico to question him about the incident.

With a report from CTV Montreal's Tarah Schwartz