Police say boxes of documents containing personal information from the Walter Reed Army Institute of Research were supposed to be shredded but instead turned up last week in an off-base trash bin. A resident of a suburban Washington neighborhood near the Army medical research's campus found "numerous boxes" in the trash receptacle on Friday and alerted Montgomery County police.
Officers eventually returned the boxes to the research center.
A spokeswoman for the U.S. Army Medical Command says the files were research study records.
An investigation is under way to determine precisely what information they held and why they appeared off base.
Police say most were from the late 1990s and were likely placed in the bin on Friday.
The records were supposed to be shredded by a Walter Reed research division employee.
No foul play is suspected and no charges were filed.
Police do not believe anyone had access to the information other than the person who found the records and called authorities.