ABC

An oil processing plant on board an offshore facility off Western Australia's Pilbara coast has been shut down because of safety concerns.

The National Offshore Petroleum Safety Authority (NOPSA) has issued a prohibition notice to the operator of the Four Vanguard floating production, storage and offtake vessel.

NOPSA acting chief Ted Kirkbridge says inspectors visited the facility recently.

"There is some processing of the oil done on board the facility and as a result of an inspection, NOPSA inspectors were concerned about the ability to safely shut down and depressurise the plant," he said.

"That's why we issued the prohibition notice."

The plant will remain closed until the safety concerns are addressed.