At least 16 people were killed and five others are missing on Sunday during a 100-kilometer (62-mile) mountain marathon cross-country race in northwest Gansu Province, China, according to media reports.

Extreme cold hit the region during the race held Saturday morning in the Yellow River Stone Forest tourist site in Jingtai County, Baiyin City, said state-run Xinhua News.

Rescue efforts to find the missing persons are underway and the race has been halted.