The marine helicopter had been carrying two pilots when it ditched into the ocean about 30km from the mining export hub of Port Hedland around midnight on Wednesday.

The second pilot was picked up from a life raft by the crew of a pilot vessel about an hour after the crash and taken to South Hedland Hospital with minor injuries.

He has since been discharged.

The EC-135 chopper had been approaching the China-bound bulk carrier MV Squireship in the shipping channel to collect a marine pilot when the crash occurred.

The Australian Maritime Safety Authority detected a stress beacon, while four flares were also seen in the area shortly after the crash.

Seven aircraft and seven vessels searched on Thursday for the trainee pilot, who was reportedly flying the helicopter, and searchers be assisted by police divers on Friday.

Debris from the helicopter has been found.

The two pilots are employees of Mackay Helicopters, a subsidiary of Aviator Group.

"Our focus is on assisting with the ongoing search effort and supporting our staff and their families affected by this accident," Aviator Group's chief executive Ian Vanderbeek said.

The Australian Transport Safety Bureau is investigating.