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NEW: 112 passengers and crew members have been sickened on Celebrity Infinity

NEW: 116 people sick on a second ship, Royal Caribbean's Legend of the Seas

CDC is investigating causes

CNN  — 

Gastrointestinal illness has gripped 112 people on the cruise ship Celebrity Infinity, according to a report from the Centers for Disease Control.

Of the ship’s 2,117 passengers, 106 have suffered from vomiting, diarrhea and other symptoms, the CDC said. The illness has also affected six members of the 964-person crew.

The CDC determined Monday that the outbreak was caused by norovirus. Two staffers from the agency boarded the West Coast-based ship Monday in San Diego.

The Infinity left San Diego on March 29. It made its last stop in Puerto Vallarta, Mexico, on April 10, according to MarineTraffic.com.

Celebrity Cruises has been taking action since the outbreak began, including increasing cleaning and disinfection procedures, keeping passengers informed and taking specimens from the afflicted for testing by the CDC, the agency says.

This is the third time the Celebrity Infinity has suffered an outbreak of gastrointestinal illness, with others occurring in 2006 and 2013. The ship was built in 2001 and refurbished in 2011.

On Monday, the CDC also put out a report on another San Diego-bound ship, Royal Caribbean’s Legend of the Seas. Of the 1,763 passengers on that ship, 114 have reported ill with vomiting and diarrhea, according to the CDC. Two crew members have also been affected.

The cause of the Legend of the Seas outbreak is unknown.

The ship is due into San Diego on Tuesday.