A mystery gastrointestinal illness has spread aboard a cruise ship and now as many as 154 aboard are experiencing symptoms such as diarrhea and vomiting.

The U.S. Centers for Disease Control and Prevention is in the midst of investigating the massive outbreak on the Queen Victoria, operated by Cunard Cruise Line, a British shipping and cruise line based in Southampton, England, according to ABC.

The vessel, which is carrying 1,824 passengers and 967 crew members, left from Fort Lauderdale, Fla., on Jan. 22 and is set to reach its final destination of Honolulu, HI on Feb. 12.

The cause of the illnesses is still unknown, according to the CDC.

On Friday, it was reported that 139 were infected with the illness, but that number has increased on Saturday to 154, a total of 129 passengers and 25 crew members. 

Cunard Cruise Line confirmed that “a number of guests had reported symptoms of gastrointestinal illness on board” and they are enacting protocols to ensure the “wellbeing” of those on board,” the outlet reported.

The CDC’s Vessel Sanitation Program is keeping tabs on the situation and looking into the ship’s response and protocols.