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Two senators are asking the Pentagon to investigate claims by female soldiers at Fort Leonard Wood, Missouri, that senior commanders discouraged them from reporting additional sexual assaults.

The allegations emerged during the trial of a drill sergeant at the base who was convicted of sexually assaulting eight female trainees under his command.

Senators Claire McCaskill (D-Mo.) and Kirsten Gillibrand (D-NY) have written Defense Secretary Chuck Hagel to urge that the "troubling allegations" be investigated.

"We are deeply disturbed by media reports of the testimony of a victim and witness during this court martial that they and those around them were discouraged from reporting sexual assaults by their leadership," they wrote in a letter sent to Hagel on Tuesday.

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They cited media reports of the testimony of two female witnesses at the court martial of Staff Sergeant Angel M. Sanchez for sexually assaulting and abusing female solders he was training at Fort Leonard Wood. Last week, a military judge found Sanchez guilty and recommended a twenty year prison sentence. The sentence must be approved by the post's commander.

One of the witnesses alleged that a lieutenant colonel at the base "told her company of trainees several months ago not to report allegations of sexual assault." That witness says she now has "issues of trusting those who are in charge of me."

Another female witness testified that her unit's Command Sergeant Major told her company of Military Policemen several months ago that "if any more sexual assault cases come forward" the whole company of soldiers would not graduate from advanced individual training.

McCaskill and Gillibrand urged Hagel to begin an investigation saying " If none has been opened, we request that you open one immediately and keep us informed of the progress of that investigation. We know that you share our desire to eliminate this scourge from the military."

"The Department has received the letter from Senators Gillibrand and McCaskill, and will respond promptly and directly to them," said Pentagon spokesman Major James Brindle. "We appreciate their concerns regarding this issue."

An Army spokeswoman said that the U.S. Army's Training and Doctrine Command had previously conducted an investigation that included a review of issues such as command climate in the unit, particularly as it related to the training, procedures and enforcement of sexual assault prevention program.

"The investigation also examined whether unit command statements to trainees were proper and allegations reported as required. The Headquarters Department of the Army is now in receipt of that investigation and is reviewing it," the spokesman said.

Both McCaskill and Gillibrand have been at the forefront of reforming procedures for how the military tackles sexual assault in the military. They have been at odds particularly over Gillibrand's legislation that would have taken military commanders out of the chain of command in deciding whether to prosecute sexual assault in their units.

In the end, the Senate supported McCaskill's legislation that among other things said the "good soldier" defense should not be a factor for commanders in determining if a case should proceed to prosecution.