A further six crew members aboard the Darya Krishna ship docked in the West Australian port of Fremantle have tested positive to coronavirus.
They are isolating aboard the bulk carrier, with authorities yet to decide on whether to bring some crew ashore to quarantine.
It takes the number of positive cases from the ship to nine, including three who remain in Perth's Fiona Stanley Hospital after being transferred on Monday.
One man is in intensive care in a serious but stable condition while the other two are stable in a respiratory ward.
There were no other new cases detected on Wednesday in the community or in hotel quarantine.
WA Health is monitoring 10 active cases, excluding the six new infections which will be included in Thursday's official tally.
Six of the active cases are crew from the BBC California vessel which is also berthed at Fremantle Port.
WA's borders remain closed to residents of NSW, Victoria, Queensland and South Australia.
Victoria and SA emerged overnight from lockdowns, while Queensland residents have been free since earlier this month.
WA has typically required other states to go at least 14 days with no new community cases before loosening its border restrictions.
But with NSW recording almost 350 local cases over the past two days, Health Minister Roger Cook has indicated WA won't rush to open up to the eastern states.
"We will wait for the advice from the chief health officer," he told reporters on Tuesday.
"Obviously the situation is still fairly fluid, particularly with the NSW circumstance, so I think we'll be proceeding with a greater level of caution on this occasion."
Two staff members at Fiona Stanley Hospital have been declared close contacts after they inadvertently entered a service lift that had been used to transfer the man to the ICU ward.
Authorities say the hospital workers - a technician and a cadet nurse - had opted not to be vaccinated. They will spend 14 days in hotel quarantine.
It is the third breach in as many months involving WA hospital staff entering potentially contaminated lifts used to transfer infected patients.
"This is very disappointing and I'm not going to make excuses - it is simply not good enough," Mr Cook said.
Mr Cook renewed calls for the federal government to clamp down on ships such as the Darya Krishna and BBC California which had both visited virus-plagued Indonesia before docking in Fremantle with infected crew on board.
"We want the Commonwealth to take a tougher stance with boats that are originating from Indonesia," he said.
"We can't have this situation where we continue to see infected crew members coming into our ports and representing a risk to the people of Western Australia."
Australian Associated Press