Dozens of rusting barrels unearthed on former U.S. military land in Okinawa City have been identified as containing chemical precursors to defoliant Agent Orange, a toxic compound used widely in the Vietnam War and blamed for poisoning that has resulted in birth defects and other health problems.

Dug up more than five months ago, the 61 barrels contain three signature components of Agent Orange: the herbicides 2,4,5-T and 2,4-D, and the highly toxic TCDD dioxin, according to two independent teams of experts representing Okinawa City and the Okinawa Defense Bureau respectively.

It is the first time that all three ingredients have been identified on former U.S. military property on Okinawa.

About half of the 61 barrels bore markings of the Dow Chemical Company, one of the largest manufacturers of Agent Orange for the U.S. military.

The presence of the three chemical precursors “unequivocally defines at least some of the media sampled as being contaminated with this defoliant,” said environmental biologist Wayne Dwernychuk, who has studied the impact of Agent Orange in Vietnam.

“Dow Chemical markers on the drums further contribute to this conclusion that the original contents of some of these drums was Agent Orange,” he added.

Katsuhisa Honda, a defoliant and dioxins specialist at Ehime University, goes further, saying the results prove without doubt that defoliants were buried at the dumpsite.

The Pentagon has denied Agent Orange was present on Okinawa, despite testimony from more than 250 U.S. veterans who say they were sickened by the defoliant on the island during the Vietnam War.

A 1971 U.S. government report on Agent Orange cites the presence of a herbicide stockpile at Kadena. The site where the barrels were found was part of the base until it was restored to civilian use in 1987.

The Okinawa City investigation team reported that all 61 barrels contained traces of dioxin and that some standing water at the site contained dioxin at levels 64 times the safe limit. However, dioxin readings from the soil were within permitted limits and there was no evidence of contamination of the water table. Twenty barrels also contained traces of toxic polychlorinated biphenyls (PCBs), which have been linked to cancers and can damage the nervous, immune and reproductive systems.

Although the Okinawa Defense Bureau’s tests detected Agent Orange’s three telltale ingredients, the department stopped short of declaring that the barrels contained the defoliant itself. Its report, released on July 7, said the barrels were not labeled as defoliant and that 2,4,5-T was widely used as a herbicide at the time in Japan.

The findings provide little comfort to some on the island.

“Although the Okinawa Defense Bureau says it cannot conclude that these are defoliants, local residents’ worries haven’t been dispelled,” said Masaharu Noguni, the Mayor of neighboring Chatan Town. “There is testimony from U.S. veterans. (The bureau) should investigate the full extent of the toxic substances and remove them.”

The U.S. military had no immediate comment. United States Forces Japan director of public affairs Lt. Col. David Honchul said commanders had not yet received the Okinawa Defense Bureau’s findings.

An excavation last year unearthed more than 20 other barrels at the same site. They, too, contained high levels of dioxin — causing concerns among the parents of children who attend two on-base schools nearby. In response to their demands, Kadena officials conducted surface soil samples of the school playing fields and concluded that they posed no risk to human health.

However, this week’s findings may reignite parents’ worries.

“In light of the latest test results, I hope Kadena officials might be willing to acknowledge that base and local residents’ concerns about potential exposure to dangerous chemicals are legitimate,” said Jannine Myers, whose child attended one of the schools until recently. “We want to know if they are now going to change their stance and do something that will give residents a greater reassurance of their safety.”

At a town hall meeting at Kadena Air Base in January, Brig. Gen. James Hecker, the 18th Wing commander, reassured parents that he would do all he could to ensure that military families are safe. He added that the military would be more forthcoming with information.

However, U.S. forces have blocked subsequent attempts under the Freedom of Information Act to obtain the documents upon which Hecker and spokesman Honchul based statements on how the land near where the barrels were unearthed had previously been used.

The discovery of the barrels is the latest in a number of incidents this year that raised questions about health and safety practices on Kadena Air Base.

In March, The Japan Times reported that base officials had kept secret a large spill of PCBs in the late 1980s.

In May, Air Force officials admitted that drinking fountains were dispensing water contaminated with lead, in a building used to check children for developmental problems. The poisoning had continued from 2010 to 2014 and it is unknown how many people have been affected.

Meanwhile, military veterans have told The Japan Times that the burial of surplus chemicals — including Agent Orange — was standard operating procedure for the U.S. military on Okinawa. Large caches of barrels suspected to have been defoliants were uncovered on Marine Corps Air Station Futenma in 1981 and on former military land in Chatan in 2002. No tests were conducted for Agent Orange in either case.

Japanese authorities now plan to widen the area of excavation in the city of Okinawa to determine whether any barrels remain.

Under the U.S.-Japan Status of Forces Agreement, the military is not obliged to clean up pollution at its bases. However, growing public awareness of the problem and anger at inaction has prompted both Washington and Tokyo to address it. In late June, officials met in the U.S. for a fourth round of meetings to discuss adding environmental clauses to the agreement.