Americans began leaving a quarantined cruise ship in Japan on Monday to board chartered flights home as the number of new coronavirus cases diagnosed on the vessel jumped to 355.

The evacuation came as Japanese authorities stepped up warnings over the deadly outbreak, urging citizens to avoid crowds and “nonessential gatherings.”

The Diamond Princess was placed in a 14-day quarantine in early February after a former passenger tested positive for the virus.

But U.S. authorities announced Saturday they would offer Americans on board the option to leave the ship and fly home, where they will face another 14-day isolation period. Several other governments have announced plans to remove their citizens from the ship as well.

Late Sunday and into the early hours of Monday, Americans who opted to leave were brought off the ship in groups, passing through a makeshift passport control but undergoing no health checks, American passenger Sarah Arana told AFP.

They boarded buses driven by personnel in head-to-toe protective suits and were told that the more than a dozen vehicles would travel in a convoy.

Earlier Sunday, health minister Katsunobu Kato said 1,219 people on the ship had now been tested for the virus, with 355 diagnosed with the illness.

Japan has not been able to test all those on board due to limited supplies of testing kits, facilities and manpower, which are also needed by authorities tracking the spread of the virus on land.

But the health ministry said Saturday that passengers older than 70 are being examined and those testing negative and in good health will be allowed to leave the ship from Wednesday.

Tests on younger passengers were expected to start Sunday and healthy people will be allowed to disembark after Wednesday, it said.