The Nagasaki prefecture official said 57 more crew had tested positive, bringing the total infections on board the Costa Atlantica to 148, roughly one quarter of the vessel’s 623 crew members.
Authorities began testing after one crew member tested positive for the virus earlier this week. No passengers are on board the vessel, which has been docked in Nagasaki in southwestern Japan since February for repairs and maintenance after the pandemic prevented scheduled repairs in China.
The official told a news conference that the prefecture was discussing with the national government how to handle the large number of positive infections on the ship.
He added that there was no change in plans to send those testing negative to their home nations as soon as possible.
The infection cluster on board the vessel comes as hospitals are running out of beds in some parts of Japan, where the national tally of virus cases has risen above 13,000. Some 350 people have died. Nagasaki, excluding the ship figures, has seen a relatively low number of 17 infections and one death.
Of those infected on board the Costa Atlantica, only one crew member has been admitted to hospital, while others remain on board, having shown slight or no symptoms.
Nagasaki authorities had quarantined the vessel on arrival, and ordered its crew not to venture beyond the quay except for hospital visits.
But prefecture officials said earlier this week that some of the crew had departed without their knowledge, and sought detailed information on their movements.
The cruise ship infections follow a similar incident earlier this year, when more than 700 passengers and crew tested positive for the virus on the Diamond Princess cruise liner docked in Yokohama.