Many survivors of the deadly gas blowout in southwest China's Chongqing Municipality display obvious signs of poisoning by sulfurated hydrogen, say doctors from the hospital treating victims.

The victims suffered mainly from acid burns on their skin and through the respiratory system, which was particularly difficult to treat and could lead to lung hydropsy and death due to collapse of the respiratory system, said Doctor Li Hongjun at Kaixian People's Hospital.

A large-scale search for survivors has found hundreds of victims within 10 kilometers of the gas field. The search was expected to finish at 7 a.m. Saturday, said rescue headquarters.

Most of the people killed in the gas blowout Tuesday at a natural gas field in southwest China were residents living near the blown well, said sources with the Chongqing public security bureau.

The accident left 191 people dead. Rescuers found 182 bodies Thursday and only two of them were identified as workers at the natural gas field. Nine people died in hospitals or on the way to hospital.

The natural gas field, operated by the China National Petroleum Corporation, is 337 kilometers northeast of Chongqing Municipality. The accident took place Tuesday night when a well blew out suddenly and released a high concentration of natural gas and sulfurated hydrogen.