US identifies Soviet 'yellow rain' toxin

Charges by Secretary of state Alexander Haig that the Soviet Union waged biological warfare in Indochina refered to a "yellow rain" dropped by planes in Laos and Cambodia, official sources report.

The US has known since 1976 such weapons were used by Vietnam and Laos, but sources indicated Washington now has conclusive evidence identifying the substances and will wage a campaign against their use. The US identified the agent used as the deadly trichothecene toxin, or T2, a yellowish substance found in nature for which there is no antidote.

Vietnam and Laos are cleint states of the Soviet Union, which signed a treaty banning biological weapons.