The Environmental Protection Agency in Guam says it is treating allegations that the toxic chemical, Agent Orange, was used there during the Vietnam War with the utmost urgency.
Guam Photo: Supplied
Its investigation follows a request by Guam's Governor, Eddie Calvo, for a full battery of tests on drinking water and soil after a US veteran told media he personally sprayed the herbicide on the island during the war.
EPA spokesperson Nic Lee said an investigation was underway and it was gathering testimonies from US veterans.
"The dioxin that's associated with Agent Orange is something that the World Health Organisation determines as a persistent organic pollutant and it is a known carcinogen...so we are definitely taking this very seriously."
Nic Lee said it was too early to say how long the investigation would take.
The United States military has denied using the hazardous defoliant on Guam.