Fifty-seven people in Vietnam's central province Thua Thien Hue were hospitalized with skin blisters this week after exposure to a chemical agent left behind from the American War.

By Tuesday evening, the Hue Central Hospital admitted 57 patients, 45 of them primary pupils, with the same blistering skin symptoms.

Victims reported they had exposed themselves to liquids in an oil drum which went adrift in flood waters recently, said Nguyen Duc Long, head of dermatology department of health center in Huong Tra district of the province.

A man living in Trieu Son Trung village in Huong Toan commune of Huong Tra district name Tuan said picked the oil drum during a flood in 1999 and kept it in his warehouse.

Recently, he and his son Quoc took the drum to the Huong Toan primary school No.2 to rinse it and clean and sell to scrap dealer, Truong Cong Thanh.

All those in contact with the drum suffered from skin burns and blistered skin.

Colonel Nguyen Van Dung, vice chief of military unit in Huong Tra district, explained result of sample tests showed the liquid is a kind of extreme toxic chemical left by the US army who used it in the war in Vietnam before 1975.

The toxic substance is listed as HT agent, which is grouped in highest risk class.

HT which is codenamed Runcol by the British, is a blend of 60% sulfur mustard (HD) and 40% T (nitrogen mustard) - a related vesicant with a lower freezing point.

According to Wikipedia, HT is a class of related cytotoxic, vesicant chemical warfare agent able to blister exposed skin.

Within 4 to 24 hours the exposure develops into deep, itching or burning blisters wherever the mustard contacted the skin; the eyes if exposed become sore and the eyelids swollen, possibly leading to blindness.

At very high concentrations, if inhaled, it causes bleeding and blistering within the respiratory system, damaging mucosal membranes and causing pulmonary edema.

Blister agent exposure over more than 50 percent of the human body is usually fatal.