FORT CHIPEWYAN, Alta. -- A team of scuba divers was being called in Thursday to help in the search for four hunters missing in northeastern Alberta.

The Mountie dive team from British Columbia was to arrive in the area north of Fort Chipewyan in the afternoon.

Police said the divers would work with boats equipped with sonar to search beneath the surface of the Rocher River.

On Wednesday, RCMP and Parks Canada shifted their efforts to a recovery operation after failing to find the men in the rugged bush.

The hunters left Fort Chipewyan on Sunday night in a boat, which was later found in the river that flows through Wood Buffalo National Park.

Earlier this week, more than 70 people took part in the search which included three helicopters and volunteers from the Mikisew Cree and Athabasca Chipewyan First Nations.