A helicopter flying between an offshore oil platform and mainland Norway crashed into the North Sea, killing one person and injuring five others, two of them seriously, authorities said Thursday.

The Sikorsky S-92 helicopter was on a training mission for state-owned oil and gas company Equinor ASA when it went down late Wednesday off Bergen, Norway’s second largest city, Norwegian news agency NTB said. There were six people on board. Police declined to release their identities.

They said five people "have varying degrees of injuries," including one whose injuries were minor, but gave no further details. The Haukeland University Hospital where the survivors were taken said two were seriously injured, including one who was in critical condition.

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At least two rescue helicopters recovered the survivors and the deceased person early Thursday.

Equinor CEO Anders Opedal called it "a deeply tragic incident," NTB reported. All six people were working for Equinor.

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Police said the fatality was a woman in her 60s, and Opedal told NTB that she was a nurse.

All helicopter flights in the area were suspended until at least 1700 GMT on Thursday.

The cause of the crash is being investigated.