KUNMING -- Twenty-two people -- mostly teenagers -- are missing after a bus full of middle school students plunged 100 meters into a river in southwest China's Yunnan Province.

Two bodies have been retrieved from the Niulan River in Qiaojia County, Zhaotong city, but they are yet to be identified, rescuers said Thursday.

The bus was carrying 31 students and four adults, including the driver, when it veered off the road as it was rounding a bend at 1:27 p.m. Wednesday.

Twenty-two students, a parent and a teacher failed to escape from the river.

Nine students, a parent and the driver were injured, four of them seriously. They were all being treated in hospital and were expected to recover, said a Zhaotong city government spokesman on Thursday.

More than 200 officials and hundreds of locals have been searching for the missing, said the spokesman.

The bus was owned by the Chongqing Technology and Business School, in southwestern Chongqing Municipality. The students were considering studying at the school and were on their way to an introductory visit.

They were due to travel from Zhaotong to Chongqing by train.

Police are investigating the cause of the accident.