Around 500 passengers will leave a cruise ship quarantined off Japan on Wednesday after testing negative for the new coronavirus that has infected hundreds on board, a health ministry official said Tuesday.

"The number (who will leave Wednesday) is changing, largely because it is up to passengers (if they get off)," the official told reporters.

"But it will be around 500 people."

Only those who have tested negative and have not been in close contact with a person infected with the virus will be allowed off on Wednesday and many disembarking will be Japanese passengers, the official said.

"They will go home on public transport but they will be taken by bus to places such as stations," he added.

Those who leave the ship will not face any restrictions, the official said.

"They won't be forbidden to go out."

But not all those who have tested negative will be getting off immediately because several countries have said they will evacuate their citizens from the ship, and many of those being offered repatriation are likely to stay on board until evacuation flights arrive.

"Crew members will get off after all the passengers leave the ship and it's still being arranged with the ship company," the health official said.

So far, 542 people on board the Diamond Princess have been diagnosed with the new coronavirus, despite a quarantine that began on February 5, shortly after the vessel arrived off Japan.

The quarantine was put in place after a former passenger who disembarked in Hong Kong in January tested positive.