Updated at 12:30 p.m. ET Wednesday

After thousands of U.S. veterans won a class action suit against the military over being used in chemical and biological testing, the Army says it will pay for their medical care. But the group's attorneys say the service is falling short of meeting its obligations and that it's withholding details veterans are seeking about what agents they were exposed to.

The Army says veterans can be treated for any injuries or diseases caused after the service used the soldiers as research subjects in the period from 1942 to 1975.

Notification letters went out to known class members on Nov. 1, the service says.

As for the size of the response, MEDCOM Public Affairs Chief Maria L. Tolleson said via email, "Two applications are in process and we have had about 40 more people call in who intend to apply."

As for how to apply for treatment or coverage through the program, the Army says its Medical Command is conducting "an exhaustive search" for veterans who may have been research subjects "so that no individual who may benefit from medical care is inadvertently omitted."

The lawsuit dates to 2009. It was filed by the Vietnam Veterans of America and other plaintiffs who wanted to know which chemical agents they had been exposed to — and whether those agents might have caused health problems. A court decided in the plaintiffs' favor in early 2016.

While the Army has sent letters to at least some of the plaintiffs, it hasn't issued broad notifications, as required by court documents.

The Army says it sent notification letters to known class-action members on Nov. 1.

As for the size of the response, "Two applications are in process and we have had about 40 more people call in who intend to apply," MEDCOM Public Affairs Chief Maria Tolleson said via email.

Tolleson said the Army is using traditional media and mailings to reach veterans who might be eligible, saying, We understand that our target group ranges in ages from mid-60s to late-80s and are likely not very active on social media."

But while those communications inform veterans that they're eligible for medical care, they're not answering veterans' questions about which specific agents they were exposed to.

The service tested more than 100 "biological and chemical warfare/threat agents and substances that mimicked these agents (simulants), as well as medications, vaccines, and other chemical and biological agent countermeasures," according to Tolleson.

"The Army still has not provided notice to test subject veterans regarding the specific chemical and biological tests to which they were subjected — and their possible health effects," says attorney Ben Patterson of the law firm Morrison and Foerster, which represents veterans in the case. Patterson says a court ordered the Army to disclose detailed information to the former soldiers four years ago, in an injunction from November 2013.

Patterson said the Army is imposing unnecessary hurdles in the process, "in an apparent attempt to discourage and prevent veterans from applying to the program and receiving the medical care to which they are entitled under the Army's own regulation."

As part of the class action lawsuit's resolution, the Army is required to use a variety of means to contact former test subjects, from notification letters and a "publicly accessible website" to public notifications and social media accounts. The service has posted its plan to uphold its obligation on the Army Medicine military website. But there's no mention of the plan on several social media accounts, including the official Army Medicine Twitter feed.

"The law firm representing the veterans estimates at least 70,000 troops were used in the testing, including World War II veterans exposed to mustard gas," NPR reported in 2015, in a follow-up to our reporting on WWII vets.

As for who's eligible for coverage, the Army lists these requirements:

One veteran, Frank Rochelle, was injected in 1968 with a drug that made him hallucinate for nearly two days. He knows its identity only by its code name — CAR 302668.

"We were assured that everything that went on inside the clinic, we were going to be under 100 percent observation; they were going to do nothing to harm us," Rochelle told NPR in 2015. "And also we were sure that we would be taken care of afterwards if anything happened. Instead we were left to hang out to dry."

Last month, Rochelle received a letter from the Army — but instead of a detailed account of his medical history, it was a form letter, telling him that if he had volunteered to receive "medications or vaccines," he might be eligible for medical care.

The military said it ended chemical and biological testing in 1975 after its chief of medical research admitted in a congressional hearing that his office didn't have any way to monitor research subjects' health after the tests were conducted.

In its FAQ about the treatment program, the Army also addressed the medical concerns of veterans who have served in more recent decades.

To the following question:

"I believe I have a disease or medical condition as a result of Army chemical or biological substance testing at FT McClellan (or other Army installations) during the 1980s (or 1990s), can I apply for medical care benefits under this medical care injunction?"

The military replies:

"No. This program is only available to former members of the Armed Forces who have an injury or disease resulting from their participation in a U.S. Army chemical or biological substance testing program."

NPR Librarian Barbara Van Woerkom contributed to this report.

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