ProPublica has sued the U.S. Department of Veterans Affairs, claiming the agency failed to promptly process a request for correspondence with a consultant about Agent Orange, a toxic defoliant used during the Vietnam War.

The lawsuit, filed late Friday in U.S. District Court in Washington, D.C., alleges that the delays violated the Freedom of Information Act, a 50-year-old law whose mission is to provide the public with information about government operations.

ProPublica submitted a FOIA request in May, requesting correspondence between various VA officials and scientist Alvin Young, who has guided the stance of the military and VA on Agent Orange and whether it has harmed service members. The request also sought internal correspondence about any contracts awarded to Young or his consulting firm.

To date, the VA has not provided any of the requested documents.

“We always try, as we did in this case, to resolve records issues without filing a lawsuit.” said Stephen Engelberg, ProPublica’s editor in chief. “The documents that relate to Dr. Young’s government-paid work are exactly the sort of material the Freedom of Information Act covers. We look forward to reporting on their contents as soon as possible.”

In a statement, the VA said it has not formally received the lawsuit and does not comment on pending litigation. It also said, “VA strives to process FOIAs on a first-in, first-out basis. Generally, requests are placed on one of two tracks: simple or complex. Complex requests, by definition are more laborious and may require more time to process.”

Young has been a staunch defender of Agent Orange, saying that few veterans were exposed to the herbicide, which contained the chemical dioxin. Some vets, he wrote in a 2011 email, were simply “freeloaders,” making up ailments to “cash in” on the VA’s compensation system. (The email was to a veteran who had been corresponding with Young and subsequently shared it with others.)

Over the years, the VA has repeatedly cited Young’s work to deny disability compensation to vets. Young’s critics, including other scientists, say that his research has been compromised by inaccuracies, inconsistencies or omissions of key facts. Some of Young’s work has been funded by Monsanto Co. and Dow Chemical Co., the makers of Agent Orange, and he served as an expert for the chemical companies in 2004 when Vietnam vets sued them.

ProPublica and The Virginian-Pilot wrote about Young’s role in the VA’s handling of Agent Orange claims in October. In the story, he defended his consulting work and his research. He said there’s no conclusive evidence showing Agent Orange directly caused any health problems. He also said he believes most sick vets are suffering from the effects of old age, or perhaps war itself, rather than Agent Orange.

The article was part of a series of articles about Agent Orange’s lasting effects more than four decades after the Vietnam War ended.

In its May FOIA request, ProPublica asked the VA to expedite its handling of the request and waive all fees. While those requests were granted, different offices within the VA have cited various reasons, including computer issues and a backlog of requests, for not producing any records.

“The VA has stonewalled and failed to disclose them,” said the lawsuit, filed on ProPublica’s behalf by attorney Seth Watkins of the law firm Adduci, Mastriani & Schaumberg, in Washington, D.C.

The lawsuit seeks an order compelling the VA to produce the records and pay its attorney’s fees.