Ontario's police watchdog has cleared a Toronto police officer who says he punched an Occupy Toronto protester in the face during an arrest.

The Special Investigations Unit says it's unclear whether the force was "excessive," when considering the level at which Angela Turvey was resisting arrest.

The SIU says Ms. Turvey, 37, had a broken nose, a black eye and required seven stitches above her right eye, but it wasn't clear whether the injuries were from the punch or her head hitting the ground during arrest.

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SIU Director Ian Scott says while he believes Ms. Turvey was punched in the face, she was interfering with the arrest of another protester and there are no reasonable grounds to criminally charge the officer.

The SIU says security video shows Ms. Turvey refusing orders to back away from police during a man's arrest, swinging at officers, then after the punch struggling on the ground with police as she is arrested.

The scuffle took place outside a downtown Toronto courthouse on University Avenue on March 30, a day when five Occupy protesters were arrested earlier when police moved to evict them from a camp set up near city hall.

The group had already been removed several months earlier from its original camp at St. James Park.

SIU investigators interviewed six officers and 14 other witnesses and examined security footage of the incident.

The agency is called in whenever someone is killed or seriously hurt while interacting with police.