Puerto Vallarta

(CNN) -- Twenty-two Carnival Cruise Lines passengers were robbed of valuables and their passports during a shore excursion in the Mexico seaside resort of Puerto Vallarta, cruise officials said late Saturday.

The passengers were robbed Thursday during a guided trail excursion, according to a statement released by the cruise line.

The cruise line did not provide details of the robbery, saying only that there were no injuries and the tour was suspended on future sailings under further notice.

"Carnival is working with guests to reimburse them for lost valuables and assist with lost passports or other forms of identification," the statement said.

The robbery comes two weeks after the U.S. State Department issued a travel warning to Americans to avoid all but essential travel to all or parts of 14 Mexican states, including the state of Jalisco. Puerto Vallarta is the sixth-largest city in Jalisco.

The State Department also warned travelers to use caution in visiting part of Baja California, Colima and Morelos.

The 3,000-plus passenger Carnival Splendor set sail February 19 from Long Beach, California, for a seven-day Mexican Riviera cruise that included stops in Cabo San Lucas and Puerto Vallarta, according to the ship's online itinerary.

The travel warnings and reports of increasing violence in Mexico have caused many cruise lines to curb their itineraries, either eliminating and shortening stops.

A number of cruise lines dropped Mazatlan from itineraries last year following a spike in violence.

Puerto Vallarta has remained a tourism hotspot, drawing college students during Spring vacations as well as cruise passengers.

The travel warnings follow reports that more than 47,500 people were killed in drug-related violence in Mexico between December 2006 and September 2011, according to the State Department. While most of those murdered were involved in criminal activity, innocent people were also caught in the crossfire, the State Department said.

Mexican President Felipe Calderon declared a crackdown on cartels in late 2006.