Ten Russian spies freed in a swap deal with the U.S. will take lie detector tests as part of an evaluation of their performances, the Moskovsky Komsomolets daily said on Tuesday, citing an intelligence service source.

After their arrival in the Russian capital, the ten were delivered directly to the headquarters of the Russian Foreign Intelligence Service (SVR), the source said.

"Specialists are currently working with members of the spy team. They are trying to find out who, and in what circumstances, could have failed," the source added.

"A variety of tests, including lie detectors, are being carried out," he said, stressing however that it would be wrong to label the investigation an "interrogation."

"If it comes to light that the SVR officers have made serious mistakes, they may be dismissed," the source said.

MOSCOW, July 13 (RIA Novosti)