Premier Mark McGowan has confirmed a FIFO worker has returned a “very weak positive” result of COVID-19.

He said it is possible the man was infectious while in the community and urgent contact tracing is now underway.

“We don’t know if he’s infectious because, to further complicated matters, this person had been COVID positive back in March and April of last year,” Mr McGowan said.

It’s believed he may have contracted the virus from a COVID-19 positive traveller from Queensland at Perth Airport on July 20, between 4am and 7am.

“We don’t actually know that he acquired it from the gentleman at the airport, but it’s the most plausible explanation we currently have.”

The FIFO worker is from FMG’s Cloudbreak mine, and was on site from July 20 to 27.

The man returned a very weak positive and then a negative test.

The worker’s girlfriend has tested negative and three close workers have also been tested, one of which has returned a negative result.

A list of possible exposure sites has been released, and sites include the Subiaco Hotel, the Indian Ocean Hotel and the Old Faithful Hotel.

Anyone who visited a possible exposure site or has COVID-19 symptoms is required to get tested and isolate until they return a negative result.

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In a statement a Fortescue Metals Group spokesperson said they are working closely with the Department of Health.

“All team members who were on site during that period are not required to isolate unless they are identified as a close contact through contact tracing,” the statement reads.

“Fortescue has a comprehensive COVID-19 management plan and protocols, as well as access to rapid antigen testing on site.”