Another two crew members aboard a cargo ship docked in Fremantle have tested positive to coronavirus as Western Australia further tightens its border controls.
The new cases mean 10 out of 14 crew members aboard the BBC California vessel have tested positive since the ship arrived.
They are all isolating in separate cabins.
Serology test results to determine whether any crew members previously had the virus are yet to be received, WA Health said on Tuesday.
The two latest positive cases had not displayed any symptoms prior to being tested as an additional precaution on Monday afternoon.
Authorities are monitoring 17 active cases, including the 10 infected crew members.
WA has reintroduced a 14-day quarantine requirement for travellers from South Australia, which will enter lockdown as of 6pm on Tuesday.
The seven-day lockdown was announced after a cluster of local cases involving the highly infectious Delta variant grew to five.
WA already has a hard border in place for NSW, Victoria and Queensland, and Premier Mark McGowan has warned SA could soon join that list.
"These changes will no doubt be disruptive and cause frustration but we need to do everything necessary to lock out this virus, especially when there are numerous Delta variant outbreaks on the eastern seaboard," he said on Tuesday.
"I urge any Western Australian that has recently travelled to South Australia to come home immediately - as the hard border may need to return if the situation escalates further."
Under WA's controlled border regime, Tasmania, the Northern Territory and New Zealand are the only jurisdictions not currently subject to quarantine requirements.
Authorities face an anxious wait to learn whether any of the BBC California crew members will require hospitalisation.
The vessel left Egypt on June 8 and has since visited three ports in Indonesia. A number of crew members became unwell last week, prompting the ship's captain to seek assistance.
The ship docked at Fremantle Port on Monday, allowing crew members to disembark in small groups so they could be tested inside a shed.
They were met by health workers and police, clad in personal protective equipment, and returned to the ship a short time later.
Mr McGowan insisted "every precaution" was taken to ensure the safety of port workers and the West Australian community.
He said anyone who needed medical treatment would be hospitalised, but doing so would increase the risk of community infection.
"If the crew can remain on board the ship and they can quarantine there, it reduces the risk to all of us," he said.
