TORONTO - Police officers will face no punishment in the cases of six people who were left with various facial and bone fractures from G20 protests.

Ontario's Special Investigations Unit looked into the complaints from six people, who allege police officers caused their injuries.

In several cases the SIU did not dispute that officers probably used excessive force, but since individual officers could not be identified, no one could be sanctioned.

When police started to advance on a June 26 demonstration at the Ontario legislature people were rushing away when a young woman fell to the ground, the SIU report stated. Brendan Latimer, 19, stopped to help her and was knocked over and trampled by fleeing protesters.

Police officers arrested him and Latimer said he was hit in the face by one of them. He was treated in hospital for a facial fracture.

The SIU concluded there are "reasonable grounds" to believe an officer used excessive force, but despite interviewing nine witness officers from the Toronto Police Service and one civilian witness, the officer who struck Latimer could not be identified.

In some of the other cases several officers declined to be interviewed for the SIU investigations, as is their right. That left the SIU in several cases unable to determine a specific officer at fault.

The SIU release details some "very serious incidents," and it's disturbing that the people injured and members of the public won't know who was responsible, said Graeme Norton of the Canadian Civil Liberties Association.

"That is troubling when you can't even identify the police officer who may have done something illegal or inflicted an injury on a member of the public," said Norton.

In many of the investigations it looks like that has been a result of the participation -- or the lack thereof -- of the officers involved or some of the witness officers."

Norton said the investigation findings are further evidence of the need for a broader look at events surrounding the G20, and why his association is calling for a public inquiry.

The SIU investigated six complaints from people who were treated for facial, arm, shoulder, nose or finger fractures after they were detained by police during the G20 summit.

Adam Nobody, 27, was also at a demonstration at the legislature and started to run away as police ordered people to move back. As he ran Nobody was knocked to the ground by an officer in riot gear and arrested. He was treated in hospital for a fracture below his right eye.

In a video posted to YouTube the man can be seen running from six officers, then once on the ground they surround him, pin him to the ground and one of them can be seen quickly moving a closed fist in a striking motion in the area of Nobody's head or upper body.

Two officers were designated as subject officers during the investigation, but they would not agree to be interviewed.

The SIU concluded there appeared to be an excessive use of force, but it's impossible to tell the identity of the officer from the video. The arresting officer couldn't be identified because the badge number on the arrest sheet didn't correspond to an assigned badge number within the Toronto Police Service.

Police began to arrest people en masse that weekend after protesters using so-called Black Bloc tactics broke away from a peaceful rally and ran through the city's downtown core, smashing windows and burning police cruisers.

More than 1,000 people were arrested during the summit. Of that group about 300 were charged and five months later few are still facing those charges.

It's believed to be the largest mass arrest in Canadian history, surpassing even the October Crisis in 1970 when martial law was imposed. The vast majority of those detained were released without charge within 24 hours.