The search and rescue mission undertaken on Wednesday has now officially been transformed into a recovery effort, the Canadian defense ministry said in a statement.

"Today, with the call to end the search and rescue mission, I join all Canadians in mourning the loss of six Canadian Armed Forces members," Prime Minister Justin Trudeau said in a statement.

So far, the body of one crew member from the Cyclone Sikorsky CH-148 helicopter, Sub-Lieutenant Abbigail Cowbrough, has been recovered and identified.

"The missing five members who were aboard the aircraft are now officially considered missing and presumed deceased," the defense ministry's statement said.

"Additional remains have been discovered during the search, but cannot be identified at this time."

The accident took place Wednesday -- the helicopter was headed back to the warship HMCS Fredericton after a training mission when contact was lost.

NATO ships and aircraft took part in the search and rescue mission, supported by Greece, Italy, Turkey and the United States.

"These units have completely saturated the area," Canadian Rear Admiral Craig Baines, commander of Maritime Forces Atlantic, said in a statement.

"We are certain that if there were survivors, we would have found them within the past 48 hours," he added.

The Canadian ministry said that "NATO allies will be continuing recovery efforts at the scene as HMCS Fredericton departs for port in Italy," where it will arrive on Saturday.

Canadian Defense Minister Harjit Sajjan said the helicopter's cockpit voice and flight data recorders had been recovered and would be analyzed in Canada.

The cause of the crash is so far "unknown," he said.

The Canadian frigate and submarine-hunting helicopter had been deployed since January 20 on NATO's Operation Reassurance, aimed at deterring Russia intervention in eastern and central Europe.