It is believed a worker at a construction site was purposely injured by another worker who threw a fire extinguisher down an elevator shaft.

An Ottawa police criminal investigation has been launched into an incident which left a construction worker with serious injuries, at a site downtown.

Ottawa Police Service Acting Chief Steve Bell receieved a letter from the Ottawa and District Labour Council (ODLC) on Friday, requesting a full criminal investigation into an August 14 workplace incident at a Claridge Homes construction project at 70 Gloucester Street.

The injured worker was hit by a falling fire extinguisher while in an elevator shaft of a partially constructed building.

Council president Sean McKenney was prompted to write the letter after an assertion made by Claridge Homes lawyer Michael Edelson that another worker "purposely and with intent to cause serious injury, bodily harm and/or death, threw a fire extinguisher down an elevator shaft, directed specifically at the [now seriously injured] worker."

Edelson has since further clarified his comment to the ODLC. He said the fire extinguisher could not "roll into the elevator shaft" because there are four-foot steel barriers at the openings to the shaft.

In a statement to OttawaMatters.com, the lawyer wrote, "Someone either intentionally or negligently would have had to lift the extinguisher up over the barrier and drop or throw it down the shaft. The extinguishers were kept in an area over approximately 20 ft away from the shaft itself."

"It is unknown to us at this time who did it, or precisely why they did it," said Edelson. "It was either an intentional act intended to seriously injure or cause death or was criminally negligent conduct."

The labour council also cited the Westray Provisions, contained in the Criminal Code of Canada since 2004, when it demanded that police conduct a full criminal investigation "at any and all construction projects when there has been a workplace fatality or serious injury."

"You are aware of section 217 of the Criminal Code of Canada in respect to 'duty of persons directing work' and the requirements by police services across Canada to investigate workplace fatalities and serious injury," the ODLC letter read.

McKenney said current Ministry of Labour investigation is a separate investigation apart from a criminal investigation by the Ottawa Police Service.