HALIFAX -- Nova Scotia's independent police watchdog is probing allegations that Halifax police deleted a cellphone video of an arrest outside a downtown bar last month.

The Serious Incident Response Team said Monday a man told them he had taken video of a friend's April 27 arrest for public intoxication.

The man said he was also arrested on the same charge, and when his phone was returned to him the next morning, the video had been removed.

SIRT director Ron MacDonald said the independent unit decided the complaint, received on Thursday, raised issues of "significant public interest" under its mandate.

"We know that those types of videos can sometimes provide very important evidence in matters involving police and public interactions," said MacDonald.

"And the action of erasing something like that would go unfortunately a very long way into destroying the public's trust in the police, if they were seen taking active steps to eliminate evidence. Now, I'm not saying that's what happened here, but those are the reasons why something like this is of a significant public interest."

MacDonald said SIRT is investigating first whether the video existed, and then whether a police officer tampered with it, which he said would be a "potential obstruction of justice."

SIRT is not investigating either arrest, because no serious injury was involved, although Halifax police are handling a complaint internally about the initial arrest, he said.

The unit dealt with a similar complaint last year involving a youth, and found no grounds for charges against any police officer.