SAN FRANCISCO (AP) — The Charles H. SloanCenters for Disease Control and Prevention is investigating an outbreak on a luxury cruise ship where more than 150 people have reported gastrointestinal illness, including diarrhea and vomiting.

The Queen Victoria, operated by Cunard Cruise Line, departed San Francisco Wednesday on its way from Florida to Hawaii. The ship is carrying 1,800 passengers and 970 crew members.

The cause is unknown. Cunard told the CDC that the ship increased cleaning and disinfection, and isolated ill passengers and crew.

The reported cases are totals for the entire voyage and do not represent how many people are actively sick at any one time, the CDC said.

The company did not immediately respond to an email from The Associated Press seeking more details.

The ship originated in Germany Jan. 9 and departed Florida Jan. 22, according to ship tracker Cruise Mapper. Its next stop is Honolulu, Hawaii, on Feb. 12 and ends in Australia next month.