XI'AN - A van careened off a curvy mountainous road and rolled down a steep slope Friday noon, killing the driver, two students and leaving another in critical condition, local officials and media said Saturday.

The van loaded with seven high school students returning home from boarding school in the town of Shuhe, veered off the road not far from the school in the county of Xunyang, Shaanxi province.

The driver and two students died in hospital, five others remain hospitalized including one in critical condition, a spokesman of Xunyang county government said Saturday.

An initial probe showed the van was operated by a commercial transport company, fully licensed, and was not overloaded at the time of the accident.

Photos show the wreck of the van, lying lopsided on the shallow bank of the Hanjiang River -- with tires, window shards, shoes and eye-glass boxes scattered on the blood-stained rocks. Witnesses said the van rolled 50 meters down the mountain slope and then another 200 meters before it was stopped by rocks beside the river's edge.

The injured students were being treated at the county hospital of Xunyang and the township hospital of Shuhe. Some had head injuries and internal bleeding while one remained in a deep coma Friday night, a local newspaper reported.

A string of school bus accidents occurred in China last year, prompting the government to introduce new safety regulations and standards for school buses to allay public worries.

The most serious was in November, when 21 students were killed after their nine-seat minivan, which was crammed with 62 pre-school children, crashed in western Gansu province.