One person died and five were injured when a helicopter crash-landed in the ocean off western Norway, police said on Thursday, leading to a temporary halt in transport to and from the country’s offshore oil and gas platforms.

The Sikorsky S-92 aircraft operated by Bristow Norway was on a search and rescue training mission on Wednesday when the accident occurred, officials have said.

The six people on board were hoisted from the sea by rescue workers, but one was later declared dead in hospital, police said in a statement on Thursday.

One of the five survivors had only light injuries while the other four had suffered varying degrees of injury, the police added.

The cause of the accident was not immediately known. Lockheed Martin LMT.N company Sikorsky, which manufactured the helicopter, said on Wednesday that safety was its top priority and that it stood ready to support the investigation.

Energy group Equinor EQNR.OL said the helicopter was a search and rescue aircraft normally serving platforms at the company’s Oseberg oil and gas field in the North Sea.

“Everyone on board the helicopter was on an assignment for Equinor. Our key task now is to help take care of those involved,” CEO Anders Opedal said in a statement.

Following the accident, Equinor halted all regular helicopter flights to its oil and gas platforms in Norway out of consideration for those affected and to get an overview of the situation.

“The company aims to get the helicopters back to normal operation quickly and is now making the necessary preparations to achieve this safely,” Equinor said.