A sample of ''yellow rain'' obtained from Laotian refugees is the hardest evidence yet of chemical weapons use against civilians in Southeast Asia, according to an ABC report.
The sample, collected by insurgent anticommunist Hmong troops in Laos, was given to an American hospital administrator in a refugee camp. He turned it over to an ABC documentary team which had it analyzed by a Rutgers University scientist.
The scientist, Joseph Rosen, said he found three deadly mycotoxins previously identified by the US government in other samples from Southeast Asia.
Mr. Rosen said he gave it to the press rather than US authorities because he didn't think the government was interested in proving charges that chemical weapons were being used against the Hmong and other civilians. Last September, however, Secretary of State Alexander Haig publicly accused Soviet-backed forces of using lethal chemicals in Southeast Asia and Afghanistan, and the government has since stepped up its efforts to support this charge.
The ABC report provides no hard evidence on any Soviet role in chemical weapons use, but it includes interviews with a communist defector and others who allege Soviet involvement.