The Darya Krishna bulk carrier had visited virus-plagued Indonesia before docking in Fremantle on Monday with infected crew on board.

So far nine positive cases have been recorded on board the ship.

The five crew and one passenger being transferred into 14 day quarantine have tested negative, but one has returned a positive result to antibody testing.

Eleven crew remain on board, of whom six have previously tested positive, and another four have positive antibody tests.

Another three crew members were taken to Perth's Fiona Stanley Hospital earlier in the week, with one in intensive care and two in a respiratory ward.

The health department said on Thursday the bus transporting the crew into hotel quarantine had mechanical problems, and the men would be transported using a replacement bus.

WA Health Minister Roger Cook has renewed calls for the federal government to clamp down on ships such as the Darya Krishna and BBC California, which is also berthed at Fremantle Port.

"We want the Commonwealth to take a tougher stance with boats that are originating from Indonesia," he said on Wednesday.

"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