TRAVIS AIR FORCE BASE, Calif. (AP) — One of two charter flights carrying cruise ship passengers from Japan landed at a California air force base just before midnight Sunday, starting the clock on a quarantine period to ensure passengers don’t have the new virus that’s been spreading in Asia.

A plane carrying American passengers touched down at Travis Air Force Base in northern California just before 11:30 p.m., local time. Another flight was headed to Lackland Air Force Base in Texas.

Japan’s Defense Minister Taro Kono had tweeted earlier that Japanese troops helped transport 340 U.S. passengers on 14 buses from Yokohama port to Tokyo’s Haneda airport. About 380 Americans were on the cruise ship.

The U.S. said it arranged the evacuation because people on the Diamond Princess were at a high risk of exposure to the virus. For the departing Americans, the evacuation cuts short a 14-day quarantine that began aboard the cruise ship Feb. 5.

The State Department announced later that 14 of the evacuees received confirmed they had the virus but were allowed to board the flight because they did not have symptoms. They were being isolated separately from other passengers on the flight, the U.S. State and Health and Human Services said in a joint statement.

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases at the National Institutes of Health, said Sunday that an infected person who shows minimal symptoms could still pass the virus to someone else.

After arriving in the U.S., all of the passengers must go through another 14 days of quarantine at the military facilities — meaning they will have been under quarantine for a total of nearly four weeks.