A cargo ship carrying seven crew members unwell with suspected COVID-19 symptoms is to dock in Fremantle.
The BBC California left Egypt on June 8 and has since visited three ports in Indonesia.
Seven of the 14 crew members aboard became unwell on or about July 12 and the captain has asked for the crew to be medically assessed.
Western Australian Premier Mark McGowan said the ship would be able to berth in Fremantle on Monday for medical assessments. A special medical team will go on board.
“We are assuming COVID-19 is on board this ship, so every precaution will be taken,” he said on Sunday.
The sick crew members are six Filipinos and one Russian, with the rest of the crew from Bulgaria, the Ukraine and Russia.
They are isolating in separate cabins and do not require medical help.
But Mr McGowan said there was a risk of a sudden deterioration in their health, which could lead to a maritime emergency.
“I would have liked this ship to return immediately to Indonesia but this wasn’t possible considering the number of ill crew members on board,” he said.
“If all the crew get sick and can’t operate the ship, can’t function out on the high seas … who knows what could happen.”
He said WA had successfully dealt with about 10 similar situations since the start of the pandemic.
“We cannot allow the virus in through international shipping,” Mr McGowan said.
The BBC California operates under the flag of Antigua and Barbuda.
WA had no new COVID-19 cases on Sunday.
The state has seven active cases, including six in hotel quarantine and one in a stable condition in a Perth hospital.