The crash, which left another 20 injured, happened on a highway in the state of Quintana Roo, located on the eastern coast of the Yucatan Peninsula and well known as home to the resort city of Cancun.

The tourists had been on a Royal Caribbean cruise ship. Its port of origin was not immediately given.

Royal Caribbean’s web site says its Caribbean cruises leave from the United States mainland or Puerto Rico.

The bus was carrying 31 passengers on a straight stretch of road with little traffic. The cause of the early morning accident was not immediately known.

The tourists were headed to visit the coastal resort town of Mahahual, which features Mayan archeological ruins. The specific site they were headed to is one called Chacchoben, the state government said. 

The nationalities of the fatalities were not given but news reports said they included Italians and Canadians.

The company operating the bus, Costa Maya, said all the passengers on the bus were from the cruise ship, plus a tour guide and the driver.

A spokeswoman for Royal Caribbean declined to discuss the road accident.

On Twitter, the company expressed its condolences. DM