More than 50 workers were in the building in the city of Wenling in Zhejiang province when it came down on Saturday afternoon, state-run China Central Television (CCTV) and the official Xinhua news agency reported.
Thirty-three suffered injuries, four of them serious, the report said. Nine others escaped and three were unaccounted for.
Xinhua said earlier the cause of the collapse was being investigated.
Photos circulating on Chinese social media showed a man being carried on a stretcher by what appeared to be police officers, while rescuers and other personnel stood on top of the rubble.
Building collapses and other industrial accidents are not uncommon in China, where many structures and facilities are old, safety procedures can be lax and rebuilding has not kept up with the country’s remarkable economic growth.
China’s top safety watchdog in May blamed poor construction and weak safety standards for a fire at a nursing home that left 38 people dead.
In April, almost 30,000 people were evacuated after a fire broke out in a Chinese chemical plant which blazed for nearly 50 hours before the flames were finally extinguished.
And in November, a fire at a coal mine in northeastern China killed 26 workers, in one of the country’s most highly accident-prone industries.