The blast happened late Monday in a steel casting workshop owned by state-run Angang Heavy Machinery in the city of Anshan in Liaoning province, a spokesman for parent company Ansteel Group said.
"The rescue work just finished. The bodies of the three missing workers have been found and now the local work safety bureau is working on the cause of the accident," Song Jiachen told AFP.
The 17 injured had been taken to hospital for treatment, the official Xinhua news agency said, citing local officials.
Workplace accidents are common in China, where bosses frequently ignore safety rules in the quest for higher profits.
Nearly 50,000 people died in work-related accidents in the first nine months of 2011, down 16 percent from the the same period in 2010, figures from the State Administration of Work Safety show.
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