Montreal city workers clean up after weekend rioting in the island's north-end. The riot is thought to have been sparked by a police shooting that left 18-year-old Fredy Villanueva dead. (Peter McCabe/Canadian Press)

Quebec provincial authorities say their investigation into the shooting of an 18-year-old by Montreal police will be thorough, professional and impartial, as calls for a full public inquiry into the incident intensified Tuesday.

The criminal investigation into Fredy Villanueva's death is expected to take between eight and 10 weeks, will "establish the responsibility of every person involved in the situation, whether it is a police officer or a civilian," said Sureté du Québec Lt. François Doré at a news conference Tuesday afternoon.

"The investigation will be complete, will be impartial, will be …fair with regards to the evidence and the people involved," he said.

Provincial police will follow protocol and make sure every person allegedly involved is questioned, including the two Montreal police officers, Doré said.

But authorities have to meet with eyewitnesses and neighbours first to "verify the facts, and the scenes," before interrogating the pair of officers involved in the alleged confrontation that set off a firestorm in Montreal North on the weekend, he said.

Provincial police spoke out about the shooting investigation hours after a prominent Montreal race relations group called for a full-blown public inquiry into Villanueva's death.

The Centre for Research-Action on Race Relations (CRARR) fears the provincial police investigation into Villanueva's death won't provide a proper explanation for the shooting, believed to have triggered a riot in Montreal North Sunday night.

Quebec's policy of having one police force investigate civilian fatalities involving another police force carries no guarantee the investigation will be transparent, said the CRARR.

'An archaic notion'

"The notion of police investigating police in cases involving blunders is an archaic notion," said Montreal lawyer René St. Léger, CRARR's former director. "It has no place in a post-modern society."

A public inquiry would allow eyewitness testimony, and could establish motive, analyze police tactics and training methods, and explore possible socio-economic factors that may have contributed to the weekend events, St. Léger said.

It would also provide Villanueva's family with a sense of justice and dispel any suspicion of a coverup, he said.

Villanueva was shot by police Saturday night after he and a group of friends were involved in an alleged altercation with officers.

Police stated they resorted to using their guns because they felt threatened by the large group of young people.

Quiet returned Monday night

A protest held in the neighbourhood the following day descended into mayhem, with dozens of city blocks burning after people torched cars and garbage cans. Police officers and ambulance workers were attacked, and rioters looted stores.

Police kept a close watch on the impoverished neighbourhood Monday night with dozens of marked and unmarked police cars circling the streets.

Except for a few trash-can fires and rock-throwing, the area remained quiet.

Quebec Public Security Minister Jacques Dupuis assured the police investigation results will be released widely once they're available.

"The population wants to know what happened," he said Tuesday. "That is why I've asked the director of the Sureté du Québec to be in contact with the population as much as he can."

With files from the Canadian Press