Jan. 23 (UPI) — Three people are dead and four others are in critical condition after the helicopter they were riding in crashed during a remote ski expedition in Canada.

The crash, about 30 miles north of Terrace, British Columbia, occurred Monday during a heli-ski excursion with two other helicopters in the mountainous backcountry, according to Royal Canadian Mounted Police, who said the other helicopters lost communication before locating the crash site in a snow field.

“There were seven people on board this helicopter and, sadly, three people did not survive,” RCMP said in a statement Tuesday.

“The other two helicopters shuttled the remaining four passengers from the site, where they were met by BC Ambulance Service, Terrace Fire Rescue and taken to the hospital. The injuries sustained have been described as serious,” police said.

Northern Escape Heli-Skiing, which owns and runs the helicopters, confirmed the deaths Monday.

“The guests who ski with us and the staff who work with us each season are part of our family,” John Forrest, president and general manager of Northern Escape Heli-Skiing, said in a statement. “It is impossible to put into words the profound grief that we feel and the sorrow that our guests and our staff share.”

Police have not released any information on the victims as Canada’s Transportation Safety Board looks into what caused the helicopter to crash. Northern Escape Heli-Skiing also vowed to help with the investigation.

“Helicopter accidents are rare but do pose a risk to people who heli-ski in the mountains and backcountry. Northern Escape Heli-Skiing takes every precaution to minimize the risks while being in the backcountry, and they do this by meeting industry safety standards,” the company said.

“However, similar to many outdoor activities, it’s impossible to eliminate 100 percent of the risks posed.”