Two U.S. Navy divers from the Mobile Diving and Salvage Unit died while in the Super Pond at Aberdeen Proving Ground, Maryland in February.

Their autopsies came back Monday from the Office of the Chief Medical Examiner, with cause of death as accidental drowning.

Diver 1st Class James Reyher of Caldwell, Ohio and Diver 2nd Class Ryan Harris of Gladstone, Missouri both drowned in the 1,070 foot-long, 150 foot-deep pond dug out of the Bush River bank during a routine test on the infrastructure, Army officials told the Baltimore Sun.

The mystery surrounding the deaths comes after an additional passing of civilian engineering technician George Lazzaro Jr. at the pond on Jan. 30, while he, too, conducted some routine underwater maintenance.

His death is being investigated by the Army's Criminal Investigation Division, Army Combat Readiness Center, and the federal Occupational Safety and Health Administration.

The two men, who died on Feb. 26, were based at Joint Expeditionary Base Little Creek-Fort Story in Virginia Beach, VA, but traveled to Maryland to check out the status of the Super Pond, which is used to give the Army a place for tests on ship, boat and submarine conduct shocks.

The Defense Department, as well as researchers and private business, run experiments in this Underwater Test Facility.

Both men were apparently tied to one another on air hoses (instead of self-contained breathing apparatuses), underwater. Once they resurfaced, a source said, the two were in cardiac arrest, and were then removed from the Aberdeen Proving Ground, located about 20 miles northeast of Baltimore.

Spokesperson Bruce Goldfarb told the Associated Press that this autopsy information is the only detail released about the three men thus far.

The Army has closed the area as a result of the two incidents. No indication has been given as to when it will open up again.