A popular stretch of Outer Banks beach has been closed after storm erosion dug up “potentially hazardous” remnants of a secretive U.S. military site dating to the Cold War.

The debris is believed to be part of a U.S. Navy facility that operated from 1950s into the early ’80s, the National Park Service told McClatchy News. It was then ceded to the U.S. Coast Guard until 2005, when the facility was closed and destroyed.

“Beach erosion caused by distant Hurricane Franklin and Tropical Storm Idalia has exposed potentially hazardous infrastructure ... at the end of Old Lighthouse Road in Buxton,” the National Park Service said in a Sept. 1 news release.

“Reports of a strong smell of fuel were received from visitors. ... Seashore visitors are asked to stay out of the closed section of beach until the area is further assessed.”

Hurricane Franklin stayed offshore east of North Carolina, while Category 3 Hurricane Idalia made landfall Aug. 30 in the Florida Panhandle and worked its way northeast as a tropical storm. It excited out to sea again on the Outer Banks, which saw gusts around 55 mph and rainfall near 15 inches in spots, Dare County reports.

A photo shared by the park on Facebook shows rough surf carved a scarp several feet high into the beach, and revealed the construction material had been buried by time at the water’s edge. Details of the types of material found were not released.

The 40-acre facility was known for conducting “secret monitoring of submarines,” and included 12 buildings that were demolished after its closure, according to a 2013 report in CoastalReview.org.

“It was part of an array of sonar locations along the East Coast known as SOSUS – Sound Surveillance System – that was intended as an early warning to protect the U.S. from hostile ballistic submarines,” the review reported.

“In June 1962, the Cape Hatteras Navy base achieved the first SOSUS contact on a Soviet diesel submarine.”

Concerns have long been raised over potential hazards hidden below the surface at the site, including groundwater contamination, the review noted.

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