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 Jetstreams its fleet, both able to carry 19 passengers.
Rio Tinto chief Jakob Stausholm said 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," the CEO of the British-Australian multinational 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 RJ Simpson said.
Chief coroner of Northwest Territories Garth Eggenberger confirmed there were fatalities but said officials would not provide any further information until next of kin were notified.
The Royal Canadian Mounted Police did not immediately respond to requests for comment.
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 neighbouring British Columbia.
