XINING - Twenty-one people were killed and three others remain missing after a rainstorm-triggered flood in Northwest China's Qinghai province, said local authorities on Wednesday.

Sudden rainstorms and hail battered Wulan county in Mongolian-Tibetan autonomous prefecture of Haixi around 7 pm Tuesday, washing away more than 20 workers, said the county government.

Rescue workers take an injured person to safety, in Wulan county, Qinghai province, Aug 21, 2013. [Photo/Asianewsphoto]

The workers were repairing a construction site at the time when the tragedy happened.

As of Wednesday morning, 21 people have been confirmed dead and seven others have been sent to a local hospital for injuries.

The search for three missing people is under way.