Chinese media said that according to government officials the blast in the booming eastern province of Jiangsu occurred around 7:30 a.m. on Saturday in Kunshan city. An explosion had ripped through a workshop that polishes wheel hubs, according to media reports.
A preliminary investigation suggested that the explosion was caused by negligence after a flame was lighted in a dust-filled room, state news agency Xinhua said, adding that top Communist Party officials from the province were heading to the site.
Chinese state television identified the factory as Zhongrong Plating. Company officials could not be reached for a comment. Its website said it employs 450 workers and counts General Motors and other U.S. companies as clients. China, the world's second-largest economy, has a poor record on workplace safety. Workers are often poorly trained or ill-equipped to protect themselves from industrial accidents.
Images on China Central Television (CCTV) showed large plumes of black smoke billowing from a white low-rise building. Other images online showed the injured, many of whom appeared badly burnt, lying on wooden pallets and being stretchered on to trucks, public buses and ambulances.
By mid-day, television images showed authorities had cleaned up the blast site although a row of fire-trucks remained parked within the factory compound.
Authorities had also set up an emergency blood-donation drive in the city to assist casualties, some of whom will be taken to Shanghai for treatment later on Saturday, CCTV said.
It said when the explosion happened, more than 200 workers were at the site and 45 died immediately.
The state broadcaster said rescue work was underway and authorities were still trying to verify the number of casualties.
A fire at a poultry slaughterhouse in the northeast province of Jilin in June 2013 killed 120 people. The blaze was blamed on poor management, lack of government oversight and locked or blocked exits.