ANCHORAGE, Alaska (AP) — A rescue and recovery dive team was deployed Saturday after a helicopter with a pilot and three state workers crashed in a large lake on Alaska’s North Slope, officials said.

No survivors have been located.

“The official word is, they are missing, presumed fatal,” said Clint Johnson, the chief of the National Transportation Safety Board’s Alaska region.

An NTSB investigators was also en route to the accident scene Saturday as plans were being made to recover the wreckage from the water, he said.

The helicopter had been chartered by the Alaska Department of Natural Resources, the department said in a statement Friday. It was carrying three employees from the Division of Geological and Geophysical Survey who had been conducting field work.

“DNR is praying for our employees and the pilot, their families, and the DNR team,” the statement said. “We are continuing to await updates from the search and rescue effort.”

Natural Resources Commissioner John Boyle flew to the crash site Friday night with a North Slope Search and Rescue spotter ahead of the recovery operation, said Lorraine Henry, a spokesperson for the state agency.

The Bell 206 helicopter was reported overdue Thursday night. A North Slope Borough search and rescue team in a helicopter found debris matching the description of the missing helicopter, DJ Fauske, the borough’s director of government and external affairs, said in a text to The Associated Press on Friday.

Fauske didn’t immediately respond to messages Saturday.

The helicopter’s wreckage was found in a lake near Wainwright, which is about 50 miles (80 kilometers) south of Utqiagvik, the northernmost city in the US, formerly known as Barrow.

“The helicopter is in shallow water, it is in the middle of a very large lake,” Johnson said. “So there is a challenge as far as getting the wreckage out of there.”

The North Slope Borough requested that the Alaska State Troopers activate the Alaska Dive Search, Rescue and Recovery Team, troopers spokesperson Austin McDaniel said in an email to The Associated Press.

The team was en route Saturday to Utqiagvik, located on the coast of the Arctic Ocean about 720 miles (1,159 kilometers) northwest of Anchorage. The borough is the primary agency coordinating efforts at the crash site, McDaniel said.

The helicopter flight originated in Utqiagvik and was supposed to return there, Johnson said, adding other details of the flight were not immediately available.

The helicopter was operated by Maritime Helicopters Inc, according to a statement on the company’s website. It confirmed the accident was fatal and said names of the pilot and passengers would be released pending notification of next of kin.