The cases reported on Thursday, a woman in her 50s and man in his 30s, are both returned overseas travellers in hotel quarantine.

WA now has three active cases.

The state Labor government this week revealed under questioning in parliament the number of exemptions granted to its quarantine requirements.

Between April 6 and August 10, WA Police granted exemptions to 6661 people. Many were air crew from domestic flights, the government said.

About 42,000 people had flown into the state from overseas or interstate during the same period.

Opposition health spokesman Zak Kirkup said the figures were deeply concerning and repeated calls for the establishment of a review committee to determine the risks of the virus permeating Western Australia's closed borders.

"The public has the right to know if the government can guarantee that what is happening in Victoria won't happen here," he said.

Premier Mark McGowan dismissed calls for the review, saying there had been just four breaches identified out of 10,500 returned overseas travellers in hotel quarantine.

He said former federal health department boss Jane Halton would be arriving in WA this week to examine the hotel system.

"I think it is best at this time that we allow our lawyers, our health officials, our chief health officer and our police officers to get on and do their job," he said.

"At this point, and over the last six months, they have had done an outstanding job."

Australian Associated Press