Santiago, Chile ? A bus carrying cruise ship tourists plunged 300 feet down a mountainside in northern Chile Wednesday, killing 12 Americans, U.S. and Chilean officials said.

Two other U.S. tourists and two Chileans – the driver and the tour guide – were hospitalized in serious condition following the crash along a rugged highway near the Pacific port city of Arica, 1,250 miles north of Santiago, said Juan Carlos Poli, an Arica city hall spokesman.

“We have confirmed that all the victims were American citizens,” Poli told the Associated Press by telephone from the hospital.

The tourists were returning to Celebrity Cruises’ ship Millennium, docked in Arica, from an excursion to nearby Lauca National Park.

The driver reported that he lost control of the bus while swerving to avoid a truck approaching on a collision course, Poli said. The bus went off the narrow highway and tumbled down a steep mountainside.

He said the bus, which had a capacity of 16 passengers, “was totally destroyed.”

The accident occurred 25 miles northeast of Arica on the road leading deep into the high Andes Mountains, connecting the coast with the Bolivian capital of La Paz.

U.S. Embassy spokesman John Vance, who also confirmed the 12 U.S. deaths, said the embassy was sending consular officers to Arica.

The ship was scheduled to leave for Peru early today, but the departure was postponed in the wake of the accident, police said. He said it isn’t clear when it will leave.

A statement by Celebrity Cruises said that the tourists were sailing aboard Celebrity Cruises’ Millennium, but it was an independent private tour, not affiliated with the cruise line.

The ship was sailing a 14-night South American cruise that departed Valparaiso, Chile, on March 19 and was scheduled to conclude in Fort Lauderdale, Fla., on April 2.