One person was killed and five injured when a helicopter crashed into the ocean off western Norway, police said today, temporarily halting transport to and from the country’s offshore oil and gas platforms.

The Sikorsky S-92 helicopter operated by Bristow Norway was conducting a search and rescue operation yesterday when the crash occurred, officials said.

The six crew members were rescued by rescue teams but one of them was pronounced dead at the hospital, police said in a statement.

One of the survivors was today in a critical condition and one was seriously injured while the remaining three suffered minor injuries, the hospital where they are being treated said in a post on Platform X.

The cause of the accident is not yet known.

“We have sent accident investigators to Stavanger and Bergen to investigate the accident,” William Berthausen of the Norwegian Safety Investigation Authority told Reuters. The two cities are the main hubs for the large Norwegian oil and gas industry.