The explosion occurred as workers were sterilising the partly built tank in the city of Karamay in the Xinjiang Uygur Autonomous Region, Xinhua news agency said, warning that the death toll could rise.
Rescuers were still sifting through the destruction and trying to locate all of the workers at the accident site, Xinhua said.
The reasons for the explosion of the tank, which was being built to store crude oil, were not immediately available.
The tank belongs to Dushanzi petrochemical company, a branch of state-owned China National Petroleum Corporation.

Copyright AFP (Agence France-Presse), 2006