6:06 p.m.: This post has been updated.

In response to reports by NPR and ProPublica, a congresswoman on the House Armed Services Committee is urging the Pentagon to review decisions to deny Purple Hearts to some soldiers suffering from mild traumatic brain injuries.

In a letter sent Wednesday to Secretary of Defense Robert Gates, Rep. Chellie Pingree, D-Maine, called it "unacceptable" that Army commanders have turned down soldiers who met criteria for award of the Purple Heart, which recognizes soldiers wounded or killed in combat.

"It's absolutely heartbreaking to hear the stories of these injured veterans, whose families say they just aren't the same person since surviving a blast," Pingree said in a statement. "Just like those who suffer bullet wounds, their injuries rightfully deserve the recognition the Purple Heart symbolizes. Denying them the honor they are due because their injuries are on the inside instead of the outside is unacceptable and downright demeaning."

Army regulations (PDF) make clear that mild traumatic brain injury, also known as concussion, is among the wounds that entitle soldiers to the Purple Heart. Those suffering concussions must have received the wound during hostile action and received treatment from a medical officer.

Our story found instances in which soldiers were turned down despite well-documented blast wounds and medical treatment. We uncovered e-mails that showed some top Army medical commanders doubted whether mild traumatic brain injuries were serious enough to merit the Purple Heart. Such injuries are difficult to detect and often leave no visible signs of damage to the brain. Most soldiers recover quickly, but a minority endure lingering problems with memory, focus and concentration.

In a sign of confusion over the issue, the Pentagon's chief spokesman, Geoff Morrell, said at a press briefing last week that soldiers with concussions were not eligible for the Purple Heart. The transcript of his remarks was later corrected.

"While not every service member exposed to IED blasts will suffer the lasting consequences associated with TBI, every service member who is exposed to an enemy generated explosion and receives medical attention should receive the Purple Heart," Pingree wrote.

An Army spokesman did not immediately return a request for comment. Gen. Peter Chiarelli, the Army's vice chief of staff, acknowledged in interviews that some commanders and medical officials did not award the Purple Heart for concussions.

He asked for a legal review after NPR and ProPublica showed him a 2008 policy (PDF) issued by the top medical commander in Iraq, which appeared to contradict Army regulations by restricting which soldiers could receive the award. That review was still ongoing as of last week.

Update: A spokesman for the Army said Chiarelli said he had not seen Pingree's letter.