Tiny traces of dioxin have been found by investigators in streams near a US army base in South Korea. However there is no evidence yet to support claims that Agent Orange was buried there in 1978.
South Korean and US teams took water samples last month around Camp Carroll after US veterans said they buried large amounts of Agent Orange, a highly toxic defoliant, at the logistics base in 1978.
Seoul's environment ministry said "extremely meagre" amounts of dioxin -- within the legally permitted level -- were found in streams around the camp, which is near the southeastern city of Daegu.
South Korean officials involved in the survey said the findings do not directly show that Agent Orange was buried at the US base.
"Nobody knows for now if dioxin found this time was from Camp Carroll or not, since such amounts can be found even in normal circumstances," a ministry official told AFP on condition of anonymity.
The officials will soon begin investigations within the US army base as well, he said.
Following the veterans' claims made on US television, the US military in Korea said last month that a "large number" of drums containing pesticides, herbicides and solvents were buried at Camp Carroll in 1978.
But it said there was no specific information that Agent Orange was among the drums.
It said the materials along with 40-60 tonnes of soil were removed from the site in 1979-1980 and disposed of elsewhere.
The US has based tens of thousands of troops in the South since the 1950-1953 Korean War, with 28,500 US troops currently stationed in the country.
During the Vietnam War US aircraft sprayed Agent Orange and other herbicides containing potentially cancer-causing dioxin to strip trees of foliage, in a bid to deprive communist forces of cover and food.