The harsh measures come after a Victorian man visiting Perth tested positive to coronavirus last week.
Of the 265 passengers and crew that flew with the infected Burwood man on Wednesday’s Qantas Flight QF778 from Perth, 214 are still in Victoria with 135 of those testing negative.
So far 42 people have landed in Victoria after visiting exposure sites in Perth, all of whom are currently isolating; 32 have tested negative.
The Perth and Peel areas entered a snap lockdown set to lift from Tuesday.
WA Premier Mark McGowan said if it was not safe to open up, restrictions would remain in place.
“We just have to be cautious,” he said.
“We’re not going to make a move which will elevate the risk to the Western Australia public, our number one priority is to keep West Australians safe.
“So we won’t be opening up if we think there’s any potential for further outbreak.”
From Thursday, Perth will cut its returned traveller cap to 512 per week.
Over the past 24 hours almost 12,000 people were tested for coronavirus in WA.
In Victoria, 1464 vaccine doses were administered and 13,941 test results were received.