It is a 33-year-old mystery that has gnawed at retired sergeant Al White's conscience.

The now-former military police officer told CBC News that, before sunrise on a clear morning in the late spring of 1985, he was ordered to escort a Department of National Defence flatbed truck along an empty road at CFB Gagetown in New Brunswick. The journey took just minutes and ended in shadows just off the road, where an excavator had dug a wide, fresh pit in the spongy soil.

On the flatbed were over 40 full or semi-full barrels in various conditions. Some were solid, others were dented, rusted or in various states of decay. Almost all of them were wrapped with an orange stripe.

"At the time, I didn't think much of it," White told CBC News. "I just did the task and it wasn't until some time later that it really, really hit home to me."

Very few words were exchanged between White, the truck driver and the operator of the excavator. The barrels were dumped into the pit and covered over.

What Al White said he witnessed that morning three decades back was the burial of leftover Agent Orange, the notorious chemical defoliant linked to various types of cancer that was used in secret spraying experiments by the U.S. at the Gagetown military base in New Brunswick — something which would blow up into a major public policy issue 20 years later.

An eyewitness account

​White said he was told at the time what the barrels contained. Experts and activists who have followed the case — and who fought the federal government for compensation for military personnel and civilians affected by defoliant spraying at Gagetown — said White's statement is the first eyewitness account they've heard of the base disposing of stocks of Agent Orange.

"This is quite an interesting development from my perspective," said Wayne Dwernychuk, a expert who spent over 15 years studying Agent Orange contamination and its effects on combatants during the war in Vietnam.

Much of the public controversy in New Brunswick over a dozen years ago related to the secret spraying program. Agent Orange was sprayed at CFB Gagetown in 1966 and 1967 by the U.S. military, with permission from Canada.

It's now known that exposure can lead to skin disorders, liver problems and certain types of cancers. The Canadian government set aside almost $100 million in 2007 for Canadians harmed by defoliants at the base. In 2011, Ottawa also reversed a decision to reject compensation for dozens of soldiers and their families exposed to the defoliant who later became ill.

What makes White's account remarkable, Dwernychuk said, is that it's the first hint of an answer to a nagging question about the Gagetown spraying program: do we know what happened to all of the leftover defoliant?

Al White in uniform in the mid-1980s. "I just felt ... enough about hiding stuff. Bring it out into the public." (Submitted photo)

There are references to disposal in some of the public reports on the program — in both an independent engineering report and the public health study conducted by Dr. Dennis Furlong, which cites one instance of empty barrels being dug up near what is known as the Shirley Road dump.

White said that is roughly the area where he witnessed the burial.

There are, however, significant discrepancies between the Department of National Defence's timeline and White's account of the burial.

At least 10 sites on the base were the subject of study — and the department said it found barrels at only one.

White said he is willing to show defence officials where he saw the barrels buried; CBC News asked to accompany him. National Defence refused to allow access to the base and a spokesman said the issue has been studied exhaustively.

"DND/CAF has done extensive research into the use and testing of herbicides at CFB Gagetown and has left no stone unturned," said Daniel LeBouthillier.

LeBouthillier pointed to independent research conducted by Jacques Whitford Engineering and the community outreach the department did between 2005 and 2007.

"The Department of National Defence has been open and transparent about its work regarding this file and the science indicates that the base is safe today."

LeBouthillier did, however, invite White to contact the department directly.

Dwernychuk said the federal government needs to investigate further.

"It behooves whoever is in charge of the area, the ministry of defence, to find out what is actually in that particular region, particularly if there is a witness to the burying," he said.

The department claims it conducted remediation at the site where it found barrels. Dwernychuk said it should still look at taking deep core samples at that site, given that a brook runs through the area.

Rumours of buried toxins

Both he and Carol Brown Parker, of the Agent Orange Association of Canada — which still lobbies for more disclosure on the Agent Orange program and its aftermath — said they are amazed that White kept silent all these years.

The rumour that barrels of the defoliant had been secretly buried on the base has been rife in nearby communities for decades.

"I absolutely believe Al," said Brown-Parker, who recalled hearing as a child her teachers talking about the late night transport of barrels through the area. "It was well known they did that, but everybody kept quiet."

White said he recently lost three friends — all former soldiers — to cancer. They all suffered lingering, painful deaths, he said.

"I just felt ... enough about hiding stuff. Bring it out into the public that this did occur," White said. "Perhaps I should have brought it forth years ago after I was released from the military and I didn't, and I'm probably wrong for not doing that."

He said he would like clear, definitive answers from National Defence about the site "so that people can be at rest."

Dwernychuk said it's a bitter disappointment to hear now about what White said he saw decades past, given that he didn't come forward when the battle for recognition and federal compensation for those exposed to Agent Orange at Gagetown was being fought a dozen years ago.

"I would speculate that the government would have taken it more seriously if he had come forward earlier," he said.

"There is always going to be the question of, 'Why did you wait so long?'"