Three crew members from a coronavirus-infected cargo ship have been moved to hotel quarantine in Perth after 10 of their colleagues tested positive.
The trio, who have all tested negative, were removed on Wednesday from the BBC California vessel docked in Fremantle.
A fourth crew member who has also tested negative will stay behind because of a "critical need" for an engineer to remain on the vessel.
"He will remain isolated in a cabin on a separate deck to everyone else and will use PPE when on deck and in the engine room," WA Health said on Wednesday.
The crew members who have tested positive have previously been isolating in separate cabins with their own bathrooms.
Premier Mark McGowan said the infected crew would be allowed full access to the vessel and it would be disinfected and prepared for departure.
"Once the people on board are better and we can put the crew members who are ashore back on the ship, we obviously expect the ship to sail as soon as possible," he told reporters.
The BBC California left Egypt on June 8 and had visited three ports in Indonesia before docking at Fremantle Port on Monday.
An outbreak aboard a separate vessel which berthed in Fremantle earlier this month has added to health officials' headaches.
Nine of the 21 crew aboard the Mattina container ship have since tested positive.
The ship, also originating from Indonesia, docked in Fremantle from July 10 to 12 and is now in quarantine at the New Zealand port of Bluff.
Twenty-five maritime workers who may have come into contact with the Mattina, including at least four people who boarded the ship, are being contacted and interviewed by WA Health officials to determine their exposure.
Mr McGowan said all workers who had any contact with a vessel were required to wear appropriate protective equipment and the risk of infection was low.
But the premier will use Friday's national cabinet meeting to raise concerns about ships arriving with infected crew after travelling through Indonesia.
"Obviously banning ships from Indonesia might have other consequences and so that would be a last resort," he said.
"But certainly improving the protocols and the arrangements in Indonesian ports is vitally important."
WA has closed its border to NSW, Victoria and Queensland and reimposed a 14-day quarantine requirement for South Australian travellers as the eastern states deal with outbreaks of the highly transmissible Delta variant.
In one of the most daring escapes from hotel quarantine seen in Australia, a man this week tied bedsheets together to shimmy down a building.
The man, 39, arrived in Perth from Brisbane on Monday but was told to leave within 48 hours because he did not meet any of the exemptions for entry.
He was taken into hotel quarantine in Riverdale in Perth's inner east to await a flight out of WA.
Police allege he climbed out a window on the fourth floor and escaped down a rope made of bedsheets early on Tuesday before fleeing.
He was found about eight hours later in Mount Lawley, north of the city.
The man, who later tested negative for COVID-19, was charged with failing to comply with health directions and providing false and misleading information.
WA is monitoring 16 active cases. A record 13,577 people were vaccinated on Tuesday, 7899 of whom received their second dose.