More close contacts of an infected West Australian mine worker have tested negative to the coronavirus, with the state recording no new cases.

A seafarer aged in his 30s from the Darya Krishna cargo ship has meanwhile been placed on a ventilator after entering intensive care at Fiona Stanley Hospital last week.

No new cases emerged overnight from more than 7000 tests after it was revealed a fly-in, fly-out worker may have been infectious while in the community.

The man in his 30s returned a “very weak” positive test result in recent days but has since tested negative.

He is in isolation and has not displayed any symptoms, having previously tested positive to the virus in March 2020 after returning from overseas.

The man worked as a maintenance contractor at Fortescue Metal Group’s Cloudbreak mine in the Pilbara between July 20-27 and went on to attend venues in Fremantle, Scarborough, Subiaco and Greenwood.

Premier Mark McGowan said the man’s girlfriend, his housemate and three closest co-workers had all since returned negative tests.

A total of 83 close contacts, the majority from the Cloudbreak mine, have been identified and will be required to quarantine for 14 days.

Contact tracing has so far identified 554 casual contacts who must isolate until they return a negative test result.

“They’re doing testing of all of their staff on the [Fortescue] mine site as we speak,” Mr McGowan said on Thursday.

“By this evening, they expect to have tested everyone … obviously they’re treating the situation very seriously.”

A list of exposure sites has grown to 11, including venues in North Fremantle, South Perth and Greenwood as well as terminals three and four at Perth Airport.

• See all of WA’s COVID exposure sites here

Qantas cancelled eight flights out of Perth on Thursday after a handful of staff were forced to isolate and get tested.

Flights to Newman, Kalgoorlie, Karratha and Port Hedland were among those affected, with passengers set to be re-accommodated.

The infected man, who had been tested while in Perth under Fortescue protocols, is awaiting the results of further testing.

He is believed to have contracted the virus at Perth Airport from a Queensland man who flew there on July 20 and was subsequently denied entry to WA. That man tested positive to the Alpha variant of the virus upon returning to Brisbane.

Mr McGowan said CCTV footage showed the Queensland man, who had been wearing a face mask, walking past the mine worker whose back was turned.

“That’s, as far as we’re aware, the only interaction between the two of them,” he said.

“It’s a very, very confusing and odd case because of all these circumstances that are involved.”

Fortescue has said it is working closely with WA Health to assist with contact tracing.

Workers at the Cloudbreak site will not be required to isolate unless identified by authorities, the company said.

WA Health is monitoring 10 active cases, including five crew members aboard the Darya Krishna which remains docked in Fremantle.

Another two crew members are in hospital, including the man on a ventilator.

The BBC California outbreak has been declared over, paving the way for the vessel to depart Fremantle on Saturday after being deep-cleaned.

-AAP