PENTAGON - A newly declassified investigation says the U.S. military knew about dozens of reported human rights abuses by Afghan military and police, but used a legal loophole to keep funding the offending Afghan units.

Afghan security forces were involved in at least 75 gross violations of human rights from 2010 to 2016, including murder and child sexual assault, according to a report from the U.S. Special Inspector General for Afghan Reconstruction (SIGAR) that was requested by 93 members of Congress last year and declassified on Tuesday.

The report also notes that it was not until September of 2015, when the New York Times reported on allegations that sexual abuse of children by members of Afghan military and police forces was "rampant," that the U.S. military in Afghanistan provided related training and issued clear guidance that personnel should report suspected child sexual assault.

A U.S. law, dubbed the Leahy law, prohibits the Pentagon and the State Department from providing aid to foreign military or police units if there is credible evidence the units have carried out a gross violation of human rights.

But a clause within the Defense Department's Appropriations Act allows for an exception to this rule when support to the units is deemed to meet a "national security concern." Despite evidence that Afghan units committed violations, the Pentagon used this loophole to continue most funding for about a dozen implicated Afghan security force units.

In its report, SIGAR suggests that Congress could eliminate that exception, explaining the Pentagon has used the clause to allow the Secretary of Defense to "forgo implementation of the Leahy Law."

The Pentagon disagrees.

"The ... report does not reflect an understanding of the challenges faced by U.S. forces in Afghanistan in developing and sustaining the Afghan National Defense and Security Forces," Pentagon official Jedidiah Royal wrote in a response included in the report last year.

The investigation also raises concerns of underreported abuses. The SIGAR report said an Afghan government official expressed surprise at the low number of reported cases, noting that "most of the cases are not reported or investigated" because the police do not self-report and other people fear retaliation if they report the abuses.

According to the report, 24 of the 37 individuals and organizations interviewed said they were aware of child sexual assault incidents or related exploitation, such as "bacha bazi" boy play, by Afghan security forces. by Afghan security forces.

Afghan President Ashraf Ghani has vowed zero tolerance for "bacha bazi" in the country's security forces, and the United Nations has called on Afghanistan to swiftly prosecute state officials guilty of the practice.

The investigation found that at least three U.S. service members reported hearing what sounded like child sexual assault but did not know how to address it.