Vietnam military officials said the unpleasant gas leaked from a cylinder in central Vietnam last Saturday was corrosive hydrogen fluoride.
Upon contact with moisture, including tissue, the colorless gas immediately converts to hydrofluoric acid, which is highly corrosive and toxic and can cause blindness by rapid destruction of the corneas.
The 800 liter cylinder was bought by a local man named Bo Thang, 28, who intended to use it as material to make a car wheel pump.
But he discarded it in a field in Quang Ngai Province after smelling the unpleasant gas emitted from the tank. The gas then killed 8,800 hectares of sugar cane crops and caused eyesores to locals as it spread around a 100-meter radius.
Officials from Military Zone 5 said the cylinder label says in Chinese that it contains hydrogen fluoride.
The cylinder was buried after the pleasant gas was detected May 2 and was only uncovered for inspection by the officials, who found the cylinder half full.
There is some blurred Chinese writing on the cylinder, though its weight and size labels are clear.
Pham Truong Dung, a chemical official from the zone, said the cylinder is foreign.
As the gas was not a chemical leftover from warfare, the military will not deal with it and Quang Ngai province authorities will have to, Dung said.
Thus, the cylinder has been buried again and no gas samples have been taken for testing.
Local authorities are tracking down the seller of the cylinder.
Thong also suffered burns to his arms and belly due to gas leaked from the container.
Hydrogen fluoride is used widely in the petrochemical industry.