More close contacts of an infected West Australian mine worker have tested negative to the coronavirus, raising hopes a lockdown will be avoided.
Contact tracing is underway amid fears the 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 last year after returning from overseas.
The man worked as a maintenance contractor at Fortescue Metal Group's Cloudbreak mine in the Pilbara between July 20 and July 27 and went on to attend venues in Fremantle, Scarborough, Subiaco and Greenwood.
Health Minister Roger Cook says four of the man's five close contacts have been cleared.
"We've now had negative test results for his girlfriend, his flatmate and two of his very closest contacts at Cloudbreak," Mr Cook told ABC radio on Thursday.
"We're just waiting for the outcome of the test from the third worker he worked closely with. These are all really positive results."
All close contacts are required to quarantine for 14 days.
A list of exposure sites has grown to 11, including new venues in North Fremantle, South Perth and Greenwood, as well as the airport.
Anyone who attended those sites must get tested immediately and quarantine until they return a negative result.
"There will be a large pool of casual contacts," Mr Cook said.
"There's no reason to believe this will lead to a lockdown but there's very much cause for concern."
Qantas cancelled eight flights out of Perth Airport 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.
"It's a highly unusual situation," Premier Mark McGowan told reporters on Wednesday.
"The best explanation we have for his weak positive test result is that he probably acquired it from the man at the airport through some sort of casual contact.
"We think he was positive over the course of the last 16 days ... (but) there's a strong prospect he wasn't infectious because he was COVID-positive early last year."
Fortescue said in a statement it was working closely with WA Health to assist with contact tracing.
Workers at the site would not be required to isolate unless they were identified by authorities as a close contact, the company said.
