West Australians will be required to keep wearing face masks indoors for another week after emerging from a COVID-19 lockdown.

West Australians will be free to flock to the footy but must wear face masks under a further easing of coronavirus rules.

Some restrictions will remain for Perth and the Peel region until 1201am on Saturday May 8, Premier Mark McGowan has announced.

No locally acquired cases have been detected for the past five days after Perth and Peel completed a long-weekend lockdown.

Masks will not be required outdoors from this Saturday unless physical distancing is not possible, such as at major sporting events.

That includes Sunday's AFL western derby between West Coast and Fremantle at the 60,000-capacity Optus Stadium, which will be allowed to host a 75 per cent capacity crowd.

Cafes, restaurants and other hospitality businesses will return to pre-lockdown capacity but patrons will be required to wear face masks.

Masks are also mandatory in workplaces, for secondary school students and teaching staff and on public transport.

"If you leave your home, take your mask with you," the premier said.

The restrictions apply to anyone who has been in Perth or Peel since April 17 and subsequently travelled to another region.

Mr McGowan said the May 8 finish date ensured a 14-day incubation period from when the last local case was detected on April 23.

Two locally acquired infections were found after the virus leaked out of the Mercure quarantine hotel.

Authorities have identified 399 close contacts of confirmed cases and all have returned negative test results.

But Mr McGowan warned it was possible WA could record more locally-acquired cases when close contacts are re-tested while in quarantine.

Initial treasury estimates have suggested a $70 million hit to the economy from the lockdown.

Small businesses that incurred direct costs, such as loss of perishable goods, will be eligible for support grants of $2000.

"I know it might not be everything some businesses would want but it is an acknowledgement of the impact and some support to assist," Mr McGowan said.

Three "high-risk" quarantine hotels - the Mercure, Sheraton Four Points and Novotel Langley - will stop taking returned travellers from as early as mid-May.

It will result in an indefinite reduction in WA's cap on international arrivals, which has already been halved to 512 a week for the next month.

Opposition Leader Mia Davies said the lockdown could have been avoided had the government acted on warnings about ventilation issues within its quarantine hotels.