The bodies are thought to date from the 1930s, when Josef Stalin's NKVD secret police - the KGB's predecessors - shot scores of people in the deep, thick-walled basements of buildings near their Lubyanka HQ. This period of political purges was known as the Great Terror; hundreds of thousands were murdered or simply disappeared.
Police who examined the bodies discovered bullet holes in the skulls. "The shots were fired at close range. The wounds and the posturing suggest that the workers discovered an execution room. The bodies had been in the basement for at least 60 years," a police source said.
Sergei Baluchevsky, from the regional prosecutor's office, had another theory. "Maybe they had been killed during tsarist times or maybe they died of a deadly disease," he said.
The pistol found near the bodies dated from 1903, according to Baluchevsky, and the revolution that overthrew Tsar Nicholas II took place in 1917.
Arseny Roginsky, a Moscow historian, said in the early part of the 20th century the building next door had been home to a military conscription committee, while across the street was a military high court.
He said the military court "was perhaps one of the most important headquarters for judicial terror of the 1930s and 1940s, a most vivid time of murder when the court actively condemned people to execution on a daily basis".