BEIJING - THE death toll from explosions that ripped through a chemical plant in southwest China rose to least 18 on Wednesday, a local official said.

Twenty other people were still missing, Ms Huang from the propaganda department of the local Communist Party said. She would not give her first name as is common with officials in China.

Another 60 people were injured, she said.

The first explosion occurred at about 6 am on Tuesday in Yizhou city in Guangxi province and the blasts continued until 1 pm.

The blaze started in a workshop and spread through the plant as containers with flammable chemicals including formaldehyde and acetylene caught fire, Xinhua said.

Fire spread over a nearly 108,000-square-foot (10,000-square-metre) area, Xinhua said, citing an unidentified firefighter in the rescue operation.

The government evacuated 11,500 residents in case of further blasts and chemical leaks.

Poisonous gases, mainly sulfurated hydrogen and carbon monoxide, were still coming from the site, Xinhua quoted Ge Xianmin, Guangxi's toxic substances emergency center director, as saying.

The blast did not seriously pollute air or water in the area, Xinhua said. Rescuers set up four dams at the point where pollutants are discharged from the factory to prevent any from flowing into the nearby Longjiang River, Xinhua said.

Samples taken from the river show it is safe for drinking, it said.

Regional work safety authorities were investigating the cause of the blasts.

Mr Fan Yinfeng, an operator at the fire brigade under the Yizhou Public Security Bureau, said firefighters from nearby towns were mobilised to help.

The plant is in a development zone of Yizhou city and mainly produces chemicals for adhesives and paints, Xinhua said. It is owned by Guangxi Guangwei Chemical Co.

Thousands die each year in China from fires, explosions and other industrial accidents often blamed on insufficient safety equipment and workers ignoring safety rules. -- AP