Western Australia may have undetected community COVID-19 transmission after a woman contracted the virus from an unknown source.

Authorities are investigating where the woman may have been exposed to the virus and genomic sequencing is underway to determine the variant.

"The woman was infectious in the community but did not attend work and there are likely a limited number of potential exposure sites," WA Health said on Wednesday.

"Exposure sites will be released as soon as possible, once confirmed."

A second local case reported on Wednesday is connected to a cluster of cases involving an infected security guard at Perth's Hyatt hotel.

This person has been in quarantine throughout their infectious period.

WA is the only state or territory yet to experience significant spread of the Omicron strain, although the McGowan government's plan to reopen borders from February 5 means it is only a matter of time before such an outbreak occurs.

Four new local cases were announced on Tuesday, including a person believed to have been infected with the Omicron variant while in the community.

The person, identified as Case 1244, had close contact with a confirmed Omicron case who recently returned from Tasmania.

They subsequently spent several days in the community in Perth, with genomic sequencing expected to confirm they have the Omicron strain.

"There's a strong possibility there's been community spread of Omicron," Health Minister Amber-Jade Sanderson told reporters on Tuesday.

"This is just part and parcel of managing a really aggressive strain of this virus."

Case 1244 travelled to the airport on January 2 to pick up a family member who had returned from Tasmania.

They are believed to have worn a face mask at the airport and followed all other rules.

Perth's supermarket shelves were noticeably bare on Wednesday after Coles introduced national purchasing limits on some items.

WA will shift the Northern Territory to "extreme risk" status from Thursday, meaning travel to WA from anywhere in Australia will be blocked except under extraordinary circumstances.