A group of 12 senators on Wednesday called on the Army to investigate a recent report that the service discharged for misconduct as many as 22,000 soldiers who had been diagnosed with mental health problems.

The lawmakers, led by Sen. Chris Murphy, D-Conn., called on the Pentagon to conduct a "full U.S. Army Inspector General investigation" into the allegations, according to information from Murphy's office.

"We are troubled by recent allegations that the U.S. Army is forcefully separating for misconduct service members diagnosed with PTSD or TBI," the senators wrote in a letter to senior Army leaders. "We are concerned that it may be easier to discharge service members for minor misconduct — possibly related to mental health issues — than to evaluate them for conditions that may warrant a medical discharge."

As a result, they said, many of these soldiers will not receive "crucial" retirement, health care and other benefits, the lawmakers said. These actions also may discourage other service members from seeking the medical help they need, they said.

The Army has received the senators' letter and will respond accordingly, said Wayne Hall, an Army spokesman.

National Public Radio last month reported that the Army, since 2009, has separated 22,000 soldiers for misconduct after they returned from Iraq or Afghanistan and had been diagnosed with mental health problems such as post-traumatic stress and traumatic brain injury.

The senators’ letter was addressed to Acting Under Secretary of the Army Eric Fanning and Army Chief of Staff Gen. Mark Milley. The senators who signed the letter include Barbara Boxers, D-Calif., Ron Wyden, D-Ore., Jon Tester, D-Mont., Amy Klobuchar, D-Minn., and Tim Kaine, D-Va.

"Soldiers who deploy are at an increased risk for mental health issues, and the forceful separation of service members post-deployment only further denies treatment and support at a critical moment in any soldier's life," the senators wrote.

"We know that the health and safety of our service members and their families is your top priority, and we are confident that you will investigate these recent allegations," the letter said. "Thank you again for your service to our country, and we look forward to working with you to rectify this grave offense to the men and women that serve in our armed forces."

Army Times asked Sergeant Major of the Army Dan Dailey about the NPR report last week, when he discussed the Army's efforts to increase soldier readiness and reduce the number of non-deployable soldiers across the force.

Dailey, at the time, said every soldier's case is unique.

"It's hard to comment on that from a generalized term because there's no generalization to those things," he said. "They're individual soldier acts of indiscipline, and they're also individual care needs if they're injured, even if those injuries are not visible."

Dailey called it a tough issue.

"You've got to treat every soldier with dignity and respect, you've got to evaluate every soldier's case with regards to their propensity to serve in the future based on their condition and the recommendations from their doctor and command," he said at the time. "Commanders are given though choices."