(Adds details on Northwestern Air Lease in paragraph 2 and Rio...

(Adds details on Northwestern Air Lease in paragraph 2 and Rio Tinto statement in paragraphs 3-4)

A small plane carrying Rio Tinto RIO.L (RIO) workers crashed near Fort Smith in Canada's remote Northwest Territories on Tuesday during a flight to its Diavik diamond mine, killing some people on board.

There were no details on how many people died or how many had been on board, but Northwestern Air Lease, the plane's registered owner, said on its website it has two types of BAE BAES.L Jetstreams its fleet, both able to carry 19 passengers.

Rio Tinto Chief Executive Jakob Stausholm said in a statement that the company was devastated by the crash.

		“We are working closely with authorities and will help 
in any way we can with their efforts to find out exactly what 

has happened," Stausholm said.

Northwestern Air Lease did not respond to requests for comment, but the premier of the Northwest Territories put out a statement mourning those lost.

"It is with a heavy heart that I express my deepest condolences to the families, friends, and loved ones of those who were aboard the Northwestern Air flight that crashed outside of Fort Smith today," Premier R.J. Simpson said.

Chief coroner of Northwest Territories Garth Eggenberger confirmed there were fatalities but said officials would not be providing any further information until next of kin are notified.

The Royal Canadian Mounted Police did not immediately respond to requests for comment.

The Fort Smith Health Centre said it activated its mass casualty protocol at approximately 8:50 a.m. (1550 GMT) in response to "an aviation incident near the community," to free up resources to respond.

Three Royal Canadian Air Force squadrons supported search and rescue efforts for the aircraft, which was found near the Slave River after it lost contact shortly after take-off near Fort Smith, said Maxime Cliche, a public affairs officer with the Canadian Armed Forces.

A team of investigators has been deployed to look into the accident involving a BAE Jetstream aircraft, Canada's Transportation Safety Board said, adding that it was gathering information.

The crash comes a day after three people were killed and four others seriously injured in a helicopter crash in neighboring British Columbia.