Questions are being asked about the decision to keep thousands of passengers and crew confined on Princess Diamond following the deaths of two passengers.
The U.S. Centers for Disease Control and Prevention said the quarantine ‘may not have been sufficient to prevent transmission’.
More than 600 people onboard have been infected.
Conditions were described as ‘completely chaotic’ by a Japanese infectious diseases expert who assisted with the quarantine.
"The cruise ship was completely inadequate in terms of infection control," said Kentaro Iwata.
Chief Cabinet Secretary Yoshihide Suga admitted it was an unprecedented situation that has few pre-defined protocols in how best to handle the situation.
Health minister Katsunobu Kato said the government will look closely at how and why the quarantine was ineffective and what lessons can be learned.
Five Japanese health workers also contracted COVID-19 during their work aboard the ship.
