Officials said more than two dozen people were still missing and hundreds had been injured in Thursday's blast at the Chenjiagang Industrial Park in the city of Yancheng, in Jiangsu province on China's east coast.

The cause of the explosion was under investigation, but an editorial in the China Daily newspaper said it was likely to be identified as "a serious accident caused by human negligence".

The company, Tianjiayi Chemical Co - which produces more than 30 organic chemical compounds, some highly flammable-- had a history of safety violations and had been punished repeatedly, state news agency Xinhua said.

A team from China's cabinet, the State Council, "pledged to leave no stones unturned" during the investigation and said those found responsible would be held to account.

It called for tougher supervision over the production and storage of hazardous chemical substances and strengthened enforcement of safety regulations, Xinhua said, ordering a "comprehensive" check of safety hazards in diverse industrial sectors, it said.

At the Xiangshui People's Hospital, one of more than a dozen in the area tending to survivors, the ward corridors were filled with temporary beds for the wounded.

"I was just going to collect my wages when it blew up," said a worker who identified himself as Zuo, whose home close to the plant was destroyed by the blast.

"I don't even have a home to go to now," he said, his head covered in bloody gauze.

The hospital was relying on dozens of unpaid volunteers.

"No one is thinking about how people will pay their medical bills at the moment -- the priority is rescuing them and worrying about fees later," said one volunteer identifying himself by his surname Jiang, who was sent to help out at the hospital by his employers on Friday.

Public anger over safety standards has grown in China over industrial accidents, ranging from mining disasters to factory fires, that have marred three decades of swift economic growth.

After Thursday's blast in Yancheng, police, some wearing face masks, sealed off roads to what was left of the devastated, smouldering plant.

Windows were smashed in the village of Wangshang two kilometres (1.2 miles) away, where stunned residents likened it to an earthquake.

President Xi Jinping, who is in Italy on a state visit, ordered all-out efforts to care for the injured and to "earnestly maintain social stability", state television said.

Authorities must step up action to prevent such incidents and determine the cause of the blast as quickly as possible, Xi said.

"There has recently been a series of major accidents, and all places and relevant departments must fully learn the lessons from these," the report cited Xi as saying.

Australian Associated Press