Ontario's police watchdog is investigating a weekend arrest of a man by Toronto police outside a nightclub after the suspect's arm was injured.

The Special Investigations Unit said in a news release on Monday that the man, 18, was arrested in front of Fiction, 180 Pearl St., in the city's Entertainment District.

About 2:30 a.m. on Saturday, the SIU said the man was involved in an "altercation" with the nightclub's security staff.

Police were called, the man was arrested and his arm was injured during the arrest. According to the release, the man was taken to hospital for treatment.

"We're still confirming whether or not the injury was serious," Jason Gennaro, spokesperson for the SIU, said Monday.

Gennaro could not say if the man's arm was broken or fractured.

One Toronto police officer is the subject of the SIU's investigation, while eight other officers may have witnessed the arrest or been involved, he said.

Number of people in area during arrest

The SIU said investigators believe a number of people were in the area at the time of the arrest.

Anyone who may have witnessed the incident is urged to contact the SIU's lead investigator at 1-800-787-8529.

Also, anyone who may have any video evidence to upload that video through the SIU website.

The SIU investigates reports involving police where there has been death, serious injury or allegations of sexual assault.