The official Xinhua News Agency said the fire happened Sunday night in Wuxi, a city close to Shanghai. The bus served night shift workers at the factory.
Investigators were trying to determine what caused the blaze on the shuttle bus, the local Wuxi Daily newspaper reported on its website.
Wuxi government and party officials as well as employees who answered the phone at the Xuefeng Steel company refused to comment.
Last year, a man ignited a bucket of gasoline on an overcrowded bus in the southern city of Chengdu. The bus had sealed windows and no emergency exits, preventing escape, and 27 people died.
That fire prompted safety checks for public buses and better driver training around the country.
Road accidents also are common in China because of unsafe vehicles, poor road conditions and bad driving habits.
