State broadcaster CCTV says in a brief report that the blast in Kunshan city on Saturday morning left 65 people dead.
The official Xinhua News Agency says it occurred at 7:37 a.m. at a car polishing workshop of a metal products company.
Xinhua says more than 40 people have died and more than 120 people have been injured.
Officials are investigating the cause of the blast and working on rescue efforts and providing medical treatment.
Calls to the city's government and police rang unanswered. A man who answered the phone at the city's work safety bureau said he did not receive any information on the blast.