Two labour groups are calling for an independent investigation into the deaths of three Canadian Pacific Railway employees in a British Columbia train crash almost a year ago.

Conductor Dylan Paradis, engineer Andrew Dockrell and trainee Daniel Waldenberger-Bulmer died last February after a two-kilometre-long runaway grain train fell more than 60 metres from a bridge. The train took off near Field, B.C., about 15 kilometres west of the Alberta boundary, when its air brakes failed.

After the crash, Transport Canada ordered that all railway companies must use handbrakes when trains are stopped on a mountain grade after an emergency use of their air brakes.

The Alberta Federation of Labour alleges the CP Police Service, which is directly employed by the railway, conducted a flawed investigation.

"The deaths of these workers have yet to be fully investigated by an independent body to determine if there is any criminal liability on behalf of CP Rail," federation president Gil McGowan said in an emailed statement.

"The investigation from the outset was narrowly focused on the three workers killed and their actions, while ignoring the role CP Rail and management played."

Teamsters Canada, the union that represents CP employees, said the RCMP must be called in.

"If CP has nothing to hide, they should welcome an outside investigation for the sake of the families and all those affected by this disaster," president Francois Laporte said in a statement.

Laporte also called on the federal government to ban all forms of private policing.

"Corporate police forces have no place in the modern world," he said. "It is absurd that a company should be able to criminally investigate itself. They'll never find themselves guilty of anything."

CP Railway noted Wednesday that the Transportation Safety Board as well as Employment and Social Development Canada are doing their own investigations into the crash.

"CP is open and willing to review the facts surrounding this event with the RCMP, the TSB and other authorized agencies and continues to co-operate fully," spokesman Jeremy Berry said in an email.

Calls for the RCMP to criminally investigate CP Railway come after CBC's "Fifth Estate" investigative news program this week featured an interview with a former CP police officer. He alleged the company prevented him from obtaining key witness accounts, withheld evidence and ordered officers to keep the investigation narrowly focused on the crew.

After the program aired, the TSB's lead safety investigator on the crash told the CBC that the RCMP should investigate potential negligence by the railway company.

The TSB issued an online statement Tuesday saying it was "completely inappropriate" for its investigator to voice any opinion implying civil or criminal liability.

"(It's) very clear that it is not the function of the board to assign fault or determine civil or criminal liability," the agency said.

"The TSB advised CBC late on Jan. 27, 2020, that it does not share the view of this investigator."

The RCMP said the lead agency handling the investigation was the CP police, since the crash happened on company property.

However, the RCMP added it has the authority to investigate criminal matters across Canada and will be reviewing the case to determine its next steps.

"We are mindful that the TSB investigation is still underway and therefore we will restrict our comments accordingly," Staff Sgt. Janelle Shoihet said in a statement.

This report by The Canadian Press was first published Jan. 29, 2020