The presence of dioxin was not detected in a district in central Vietnam where the military toxin had been suspected of causing an unknown skin disease which has killed 23 people since last April.
Colonel Dinh Ngoc Tan, chief of the Military Institute of Chemistry and Environmental Sciences, announced the results after his agency finished tests on soil and water samples taken from Ba To District, Quang Ngai Province, where 239 people have come down with the disease.
Tan said his agency did not find residues of pesticides >or heavy metals.
Of the water samples taken, only the rate of microorganisms was found to exceed regulations, which means that the local water source had been contaminated, he said.
According to Tan, his agency conducted the tests in the hopes of helping the provincial health department identify the source of the mysterious ailment.
Earlier, scientists concluded that the condition was caused by chronic poisoning, but it remains unclear as to the precise toxin responsible.
Officially known as hoi chung viem da day sung ban tay ban chan (the syndrome of dermatitis and horny layer thickening in foot and hand), the disease begins with blisters on the hands and feet and decreased appetite, and can turn fatal due to organ failures, starting with the liver.