The National Security Agency (NSA) is conducting a counterintelligence probe at its Fort Meade, Md., headquarters in a top-secret hunt for a Russian agent, according to a former intelligence official close to the agency.

The former official said the probe grew out of the case of 10 Russian “illegals,” or deep-cover spies, who were uncovered last summer and sent back to Moscow after the defection of Col. Alexander Poteyev, a former SVR foreign intelligence officer who reportedly fled to the U.S. shortly before Russian President Dmitry Medvedev visited here in June.

Col. Poteyev is believed to be the source who disclosed the U.S.-based agent network.

NSA counterintelligence officials suspect that members of the illegals network were used by Russia's SVR spy agency to communicate with one or more agents inside the agency, which conducts electronic intelligence gathering and code-breaking.

One sign that the probe is fairly advanced is that FBI counterintelligence agents are involved in the search.

“They are looking for one or more Russian spies that NSA is convinced reside at Fort Meade and possibly other DoD intel offices, like DIA [Defense Intelligence Agency],” the former official said. “NSA is convinced that at least one is at NSA.”

Some of the 10 illegals who were posing as U.S. citizens helped service Russian agents working inside the U.S. intelligence community, the former official said.

No other details of the investigation could be learned.

Full story: Inside the Ring: Counterspies hunt Russian mole inside National Security Agency – Washington Times