Authorities are still searching for and waiting to clear more than 270 people who were close and casual contacts of Perth COVID-19 patients.
Western Australia on Sunday recorded no new cases of community coronavirus transmission and one additional diagnosis in hotel quarantine.
Perth and the region of Peel remain in lockdown until at least midnight Monday after two cases moved through the community, with fresh suggestions that some restrictions will be extended.
Premier Mark McGowan said 359 close and casual contacts had been identified. Of the 303 close contacts, 72 have tested negative. Of the 56 casual contacts, 13 have tested negative.
Some of the remaining 274 people are still being sought by authorities, although many have already been tested and are in isolation pending test results.
"People should get used to the prospect that some further measures will continue past Monday," Mr McGowan told reporters on Sunday.
"We need to see more testing completed. Most importantly we need close contacts and casual contacts, that is anyone who has visited the during the specific times, to be tested."
Mr McGowan said WA's quarantine hotel facilities were at capacity with 2166 people, and four more overseas flights due to land on Sunday.
The state will soon cut its cap on incoming overseas travellers from 1025 to 512 per week and Mr McGowan said the issue would be discussed at a national level.
Mr McGowan said the state conducted almost 12,000 COVID tests on Saturday, but that there would likely be an extension of restrictions, announced on Monday morning.
"It all depends on the circumstances. I can't predict what will happen. There will be an extension of some form of controls. What they are we'll work out in the morning."
The two locally-acquired cases have so far been linked to the Perth Mercure Hotel outbreak which plunged Perth and Peel into a three-day lockdown, including the mandatory wearing of face masks.
A second locally-acquired case linked to the Mercure outbreak was announced on Saturday - a man in his 40s who dined at the same restaurant as two confirmed cases.
They were a 54-year-old Victorian man who appears to have contracted the virus from a fellow returned traveller while in hotel quarantine at the Mercure and his female friend from Kardinya whom he was visiting.
Eateries at Kardinya, East Victoria Park, Morley and Northbridge are deemed high-risk sites and anyone who dined there during exposure times must quarantine for two weeks.
On Sunday, Landsdale Early Learning and Enrichment Chidcare was added to the alert list, after the man diagnosed on Saturday did drop-offs and pick-ups at the centre between Wednesday and Friday.
A Victorian man's infection was not identified until a week after he left Perth hotel quarantine and travelled to Melbourne on Wednesday.
Genomic testing has confirmed the virus initially spread in the Mercure from a couple who had returned from India to a pregnant mother and her four-year-old daughter across the corridor and remain in quarantine.
The Victorian man had been staying in a room adjacent to the couple from India.
One of his close contacts - a man in his 40s - is among the two people diagnosed in hotel quarantine on Sunday. The other is a man aged in his 50s who recently returned from overseas.
Documents released by the government this week identified the Mercure as one of three hotels considered "high risk" for ventilation issues.
WA's chief health officer received the report on 8 April and wrote to the premier last Friday advising the Mercure should stop being used.
The Mercure will soon no longer accommodate returned travellers and the government will review the continued use of the other high-risk hotels.
Mr McGowan previously criticised the Commonwealth for not providing better quarantine facilities, saying CBD hotels were not suitable.
But the federal government said alternative defence or immigration detention facilities were not as safe and did not have suitable hospital access.
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