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WASHINGTON (Reuters) - There was a rise in reports of sexual assault at U.S. Navy and Army military academies in the last year, the Department of Defense said on Wednesday.

An annual report, based on anonymous surveys, said reports of sexual assault in total across the military academies had decreased slightly in the last year, and the Air Force Academy specifically saw a decrease from 49 reports to 32.

But the Military Academy at West Point received 26 reports of sexual assault, up from 17 in the previous year, and the Naval Academy in Annapolis saw three more reports compared to last year.

“This year’s survey results underscore the unique challenges the academies face in sustaining long-term decreases in the occurrence of sexual assault,” an accompanying Pentagon statement said.

U.S. Senators grilled the Navy and Marine Corps’ top leaders on Tuesday about a scandal involving a Facebook group called “Marines United” for sharing explicit pictures of female members of the armed forces.

The Naval Criminal Investigative Service has opened an inquiry into the matter.