At least one Mexican media outlet said the passengers were returning by bus to their ship at approximately 5 p.m. after spending time in El Nogalito, a tourist area known for its lush natural setting. Masked assailants stopped the bus and robbed the cruisers of their money, watches, cameras and other valuables.
There were no injuries and all passengers were returned safely to the ship, Carnival said in a statement. Numerous authorities were notified and responded to investigate, as well as assist the affected passengers, Carnival said.
According to informador.mx.com, the bandits have yet to be apprehended.
Carnival apologized to the passengers for the "unfortunate and disturbing event" and said it is working with passengers to reimburse them for lost valuables and assist with lost passports or other forms of identification.
On Saturday, Latitude Intl, the public relations firm representing the Puerto Vallarta Tourism Board, called Thursday's robbery an "extremely rare incident." A statement on Latitude's Facebook page said, "minutes after we learned of the incident representatives from the local and state government, tourism leaders and tour operators [moved] to provide assistance to those involved and police and the district's attorney office started their investigation."
The tour in question — a guided nature trail excursion sold and booked through the line — has been suspended until further notice.
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The incident comes at a rough time for the beleaguered Mexican Riviera cruise region, which has seen numerous lines pull out over safety and security concerns, as well as issues with demand. Lines have primarily cut calls in Mazatlan, which has seen its scheduled ship visits plummet from 200 in 2010 to roughly a dozen in 2012, but Acapulco and Puerto Vallarta have also suffered.
The U.S. State Department advises Americans to exercise caution when traveling to Mexico. Earlier this month, the department released its latest travel warning, updating one that had been in effect since April 2011. As with the earlier warning, it reiterated that millions of Americans safely visit the country every year and that most of the drug-related violence occurs near the Mexico-U.S. border and along drug-trafficking routes, rather than in resort towns and other tourist destinations.
The Carnival Splendor made headlines in November 2010 after an onboard fire paralyzed the ship for three days about 200 miles outside San Diego and stranded thousands of passengers. The repaired ship set sail again last February with two new generators and a new engine.
Carnival Splendor is currently sailing on a seven-day cruise that departed Long Beach, Calif., on Sunday.
Msnbc.com contributed information to this report.
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