Perth and the Peel region have avoided another lockdown for now after no further locally acquired coronavirus cases were detected.
West Australian Premier Mark McGowan confirmed the news on Sunday, 24 hours after a hotel quarantine security guard and two of his housemates tested positive.
Contact tracers are continuing to work through the movements of the three men but all 16 close contacts identified by WA Health as "high risk" have returned negative tests.
Results are pending for a further four close contacts, while a another 136 contacts are deemed casual or yet to be classified.
All the new cases and their close contacts must quarantine for 14 days.
Sunday's AFL western derby between West Coast and Fremantle at Optus Stadium will be played behind closed doors, with the risk of 45,000 spectators travelling to the stadium deemed too high.
Nightclubs will close for the next week and all Perth and Peel residents must wear masks indoors and outdoors, regardless of proximity to others.
"We need people to get tested and we need everyone to be wearing your masks," the premier said.
"I want to avoid going into lockdown again. I know how much it can impact people's lives and businesses. But if we need to go back into lockdown, we will."
The guard in his 20s worked at the Pan Pacific Hotel between April 24 and 26 and tested positive on Saturday.
On his days off work from April 27 to 30, he moved through the community going shopping, seeing friends and visiting Mirrabooka Mosque.
He and his seven housemates were moved to hotel quarantine after he returned the positive result.
The guard had received his first dose of the Pfizer vaccine just days earlier.
Mr McGowan said the interim restrictions that had been in place in Perth and Peel following a snap three-day lockdown last weekend - including attendance limits at hospitality venues - had reduced the risk of a wider outbreak.
The guard's two infected housemates - a roommate and a guest from Canberra - had both been working as food delivery drivers.
They each worked on April 29 and 30 and could have been infectious since the 27th.
But public health advice suggested the risk was low given they were required to wear face masks and had minimal contact with customers.
Authorities are working through which restaurants they attended to collect food and if any are determined to be potential exposure sites, they will be listed on the healthywa.wa.gov.au website.
One of the positive cases attending a cooking school on the 27th and 28th with about 20 other people at the Perth College of Business and Technology.
The other students are being contacted and advised to isolate until they have returned negative tests, along with other casual contacts.
More than 3000 tests were completed on Saturday.
"We are not out of the woods as yet," Mr McGowan said.
"Our contact tracing team has a massive job underway today."
The security guard, wearing a mask, worked on the same floor as two travellers - one from the US and one from Indonesia - who were transferred to the Pan Pacific Hotel on April 24 and tested positive.
Authorities have reviewed CCTV footage and are yet to identify any concerns.
Australian Associated Press