CANCUN: A bus carrying cruise ship passengers on an excursion to Mayan ruins in southeastern Mexico flipped over on a narrow highway Tuesday, killing 11 travelers and their guide and injuring about 20 others, officials said.

Seven Americans and two Swedes were among the injured, said Vicente Martin, spokesman for the Quintana Roo state Civil Defense agency. Authorities had not yet established the nationalities of the dead.

13 remained hospitalized, six of them in Tulum and seven in the city of Chetumal, near the Belize border.

The dead were being transferred to the forensics service for identification and subsequent notification of consular authorities.

Chris Brawley, a passenger on the Serenade of Seas, was on a bus headed to the same Mayan ruins when they came on the scene minutes after the accident.

It was shortly after 9 a.m. and a convoy of buses from the cruise port at Mahahual was headed to Chacchoben, he said. They had been on the road for about 35 to 40 minutes before the accident.

Brawly said the sky was clear and the road was dry and he didn’t see any sign of another vehicle being involved in the crash, which happened on a narrow, two-lane road with no shoulder or guardrail.

13 remained hospitalized, six of them in Tulum and seven in the city of Chetumal, near the Belize border.

The dead were being transferred to the forensics service for identification and subsequent notification of consular authorities.

Chris Brawley, a passenger on the Serenade of Seas, was on a bus headed to the same Mayan ruins when they came on the scene minutes after the accident.

It was shortly after 9 a.m. and a convoy of buses from the cruise port at Mahahual was headed to Chacchoben, he said. They had been on the road for about 35 to 40 minutes before the accident.

Brawly said the sky was clear and the road was dry and he didn’t see any sign of another vehicle being involved in the crash, which happened on a narrow, two-lane road with no shoulder or guardrail.