Royal Caribbean's Navigator of the Seas was on a week-long, round-trip cruise when passengers became sick, the CDC said.

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 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