NORFOLK, Va. (AP) — Pentagon statistics released Friday show that the world's largest Navy base in Norfolk, Virginia, fielded more sexual assault reports than any other military installation last year.

But military officials cautioned that many incidents occur off base on deployment, on leave or in civilian life prior to joining up.

Naval Station Norfolk recorded 270 reports of sexual assault in 2016, constituting more than 20 percent of those recorded by the Navy.

The base is home to dozens of ships, including aircraft carriers and submarines, deploying around the globe. More than 50,000 military personnel work at the sprawling base near the mouth of the Chesapeake Bay.

"Installations with large populations tend to accumulate more reports," said Lt. Cmdr. Ryan de Vera, a Navy spokesman. "Installations with a focus on initial military training — they tend to see more 'prior to service' allegations."

The military released statistics for the last four years. During that span, reports of sexual assault at the base in Norfolk peaked at 291 in 2015.

Other bases that recorded higher numbers included Fort Hood, a U.S. Army Base in Killeen, Texas, that fielded 199 reports of sexual assault last year. Camp Lejeune, a Marine base in Jacksonville, North Carolina, received 169 reports.

The Department of Defense published the data broken down by base for the first time, releasing it after recent requests for the information under the Freedom of Information Act.

In 2012, the military "reinvigorated" its approach to addressing sexual assault and encouraged better reporting, according to de Vera, the Navy spokesman.

For instance, there has been more training and more personnel assigned to help victims.

"As a result we have seen increases in reports," de Vera said. "But no definitive statement can be made about an increase in reporting at any given installation."