ANCHORAGE, Alaska >> Alaska search and rescue divers recovered the bodies of a helicopter pilot and three scientists on Sunday from the sunken wreckage of their aircraft, which went down in a shallow lake last week on the remote North Slope, authorities said.

The cause of the crash is under investigation by the National Transportation Safety Board.

The only way to raise the wreckage will be to use another helicopter because it’s in the middle of one of the many lakes scattered across the vast tundra, said Clint Johnson, the chief of the National Transportation Safety Board’s Alaska region.

“In Alaska, here during the fire season, commercial helicopters are at a premium so we are having challenges getting a helicopter to do the work,” he said Sunday.

The dead were identified by the North Slope Police Department as Ronald Daanen, 51, and Justin Germann, 27, both from Fairbanks; Tori Moore, 26, of South Bend, Indiana; and pilot Bernard “Tony” Higdon, 48, of North Pole, Alaska.

The 1996 Bell 206 helicopter crashed Thursday while transporting the Alaska Department of Natural Resources staff while they conducted fieldwork in the area. They were members of the Division of Geological and Geophysical Survey. The helicopter is owned by Maritime Helicopters.

The wreckage was found near the small coastal town of Wainwright, which is about 50 miles (80 kilometers) south of Utqiagvik — the northernmost city in the U.S., formerly known as Barrow. The flight originated in Utqiagvik and was supposed to return there.

Volunteers from the Alaska Dive Search, Rescue, and Recovery team arrived at the crash site around 10:45 p.m. Saturday and recovered the bodies about 6 a.m. Sunday.

Authorities have said the the aircraft likely will not be raised from the middle of the 1-mile-wide (1.6-kilometer) lake until Monday or Tuesday, given the lack of available helicopters.