China says at least 191 people are dead following an explosion at a natural gas field in the southwestern city of Chongqing. Hospital workers in southwestern China's Kaixian county said they were swamped Thursday, tending to victims suffering from chemical burns and poisoning.

China's state-run news agency, Xinhua, says a gas well burst on Tuesday, sending a plume of noxious fumes, a combination of natural gas and sulfurated hydrogen, into the air.

Reports from the scene say residents within a five-kilometer radius of the explosion had to be evacuated.

News of the explosion did not reach the capital until late Wednesday, and the death toll originally was reported to be eight. It was unclear why it took so long for the incident to be fully reported.

Industrial accidents are common in China. In a report released in October, The government said 11,000 people had died at work in the first 10 months of the year.

The Chuangdongbei gas field where the explosion occurred belongs to the China National Petroleum Corporation. Company officials say an investigation was under way to find what caused the blast.

State media said President Hu Jintao told local officials to spare no efforts in the search and rescue operations. Reports said the central government had dispatched a team to coordinate the rescue efforts.