Gastrointestinal illness sickened more than 130 cruise ship passengers aboard a Royal Caribbean cruise earlier this month. The cause of the outbreak has not been determined.

The mystery gastrointestinal illness broke out onboard the Navigator of the Seas, a Royal Caribbean ship, on a round-trip to from the US to Mexico. Some 134 of the 3,914 guests fell ill, along with 11 crew members. Symptoms included sickness, abdominal cramps and diarrhoea.

The US CDC has launched an investigation after passengers on the Royal Caribbean cruise started showing signs of acute gastroenteritis (AGE), which is usually caused by norovirus