Authorities are investigating whether a truckload of an explosive used in the manufacture of fertilizer was behind the blast that killed 12, wounded 43 and left at least 300 homeless as it flattened 17 houses in southwest China's Yunnan Province on Monday.

The injured were still in hospital yesterday, and one person remained missing.

The explosion, which occurred at around 11:20 PM in the Shengangzhai area of Xinche Village in Mile County, is thought to have been triggered by an 18-ton truckload of ammonium nitrate, said police, on its way to a local fertilizer company.

Villagers alleged that a truck belonging to Li Hongwen was parked near the accident site as it usually was, but that both Li and his vehicle were unaccounted for.

Ammonium nitrate is a white solid most commonly used to produce explosives and fertilizers, and only drivers with special licenses are legally allowed to transport it in designated vehicles.

"Even these special vehicles' routes must be reported to police departments," an official from Yunnan Provincial Communication Bureau told China Daily yesterday.

The local government refused to comment on whether supervision of the storage of dangerous chemicals had been deficient.

According to China Daily, in Shengangzhai and nearby areas hazardous chemicals are handled casually and road construction workers often store ammonium nitrate alongside detonators in their work sheds.

The blast produced a crater 5.6 meters deep and 18.5 meters in diameter.

"The huge mushroom cloud that rose up made me think of an atomic bomb," said Deng Shuquan yesterday, a resident from a village about 500 meters away.

Surrounding areas were still cordoned off yesterday, and an investigation team from the provincial capital Kunming was at work. Relief work is underway.

(China Daily September 15, 2005)