XINING, Nov. 4 (Xinhua) -- Six people were killed after a trailer hit several vehicles in northwest China's Qinghai province, local police confirmed Tuesday.

The accident happened in the Haixi Mongolian and Tibetan Autonomous Prefecture at about noon, when a trailer on the national highway lost control and careered into six other vehicles.

The trailer was registered in central China's Henan Province.

Rescue work is ongoing and the number of injured is still unknown.