XI'AN, March 17 -- One person was killed and another five are missing after their vehicle plunged off an expressway into a power plant's reservoir in northwest China's Shaanxi Province on Monday night.

The incident happened in Langao County around 7:20 p.m, said the local government on Tuesday, without specifying the type of vehicle involved.

An injured passenger was hospitalized and is now in a stable condition as a rescue team is looking for the five other passengers and the vehicle in the reservoir.

An initial investigation has blamed driving while tired.