SANTIAGO, Chile (AP) -- A bus carrying tourists from a cruise ship plunged off a cliff in the highlands of northern Chile Wednesday and officials said 11 people were killed, most believed to be U.S. citizens.

Juan Carlos Poli, a spokesman for the city of Arica, 1,250 miles north of Santiago, said an undetermined number of tourists were injured.

"Rescue crews are working in the area, but we have confirmed 11 people killed, most of them from the United States," Poli said.

He said the tourists were from the Bahamas-registered Millennium cruise ship and had been visiting the area near this city in the border with Peru and Bolivia.

The accident occurred in the road between Arica and the Bolivian capital city of La Paz.

Poli said the cause of the accident had not yet been determined, but he added that the road was "very curvy ... a dangerous road."