A power plant explosion killed at least 21 people and injured five, three of them seriously, in Dangyang, Hubei province, on Thursday, according to China's top work safety watchdog.

High-pressure steam pipes at Dangyang Madian Gangue Electricity SupplyCo exploded at about 3:20 pm, killing and injuring people, the State Administration of Work Safety said in a statement.

The injured were rushed to a hospital. The cause of the blast had not yet been determined.