The Okinawa Defense Bureau recently found dioxin and other hazardous chemicals from barrels unearthed at a former U.S. military installation in the city of Okinawa, officials said Monday, suggesting they may have contained herbicides or agricultural chemicals.

The bureau, however, said the possibility that the barrels were carrying defoliants used in the Vietnam War is slim because it did not detect one of the two major components of toxic Agent Orange.

“We cannot say it was Agent Orange at this stage,” Daisuke Misawa, a bureau official, told The Japan Times.

A study conducted by the Okinawa Prefecture Environment Science Center in July detected dioxin in all 22 barrels unearthed at a municipal soccer field adjacent to Kadena Air Base in June and this month, the bureau said.

The institution also detected 2,4,5-Trichlorophenol — one of the two major Agent Orange components — in some of the barrels but failed to find the other, 2,4-Dichlorophenoxyacetic acid.

Agent Orange was mainly produced with two chemicals — 2,4,5-Trichlorophenol and 2,4-Dichlorophenoxyacetic acid — the bureau said. Dioxin was a byproduct of the process, it said.

One possibility is that the barrels may have contained herbicide, because 2,4,5-Trichlorophenol alone had been used as one in the past, Misawa said.

Another possibility is pentachlorophenol, Misawa said. Pentachlorophenol, which contains dioxin, was banned from use in agriculture in 1990.

The amount of dioxin found ranged from 62 to 1,100 picograms per gram of sample. The government’s limit for dioxin 1,000 picograms per gram of soil. A picogram is 1 trillionth of a gram.

As for soil samples taken from the site, none exceeded the government’s dioxin limit, the bureau said. But one sample contained excessive amounts of an arsenic compound and a fluorine compound, it said. The bureau plans to study the site further.

Okinawa is separately checking the soil and contents of the barrels, and its mayor plans to hold a press conference as early as Wednesday to release the results.

In June and this month, 26 decayed barrels were found in the soccer field.

The city and the bureau unearthed 22 of them but could not recover the other four, the bureau said.

As the barrels bore markings from Dow Chemical, a major defoliant producer, experts and residents are worried they may have contained Agent Orange. The site was part of Kadena Air Base until 1987.