WASHINGTON — Sergei Tretyakov, one of the world’s most famous spies of all time, is dead, WTOP has learned.

WTOP recently featured Tretyakov, who defected to the U.S. a decade ago, in the series “Escaping from the Iron Curtain.”

Results of an autopsy and toxicology tests have not been released, however his widow Helen Tretyakov confirmed the news, saying he died of natural causes in June.

Tretyakov defected to the U.S. in October 2000 after a five-year deployment in Russia’s New York mission, in charge of Russian spy activities in the U.S. and the United Nations.

The Russian spy saga that’s unfolded in recent weeks has fueled speculation that Tretyakov was somehow involved and prompted many to wonder why he had not been heard from.

Ten operatives pleaded guilty in New York to working as foreign agents in the U.S. and were deported to Russia Friday. They were part of a U.S.-Russia spy swap.

Despite the medical confirmation that no foul play was involved, some intelligence sources question the coincidence of his death and the arrest of the 10 spies.

Helen Tretyakov told WTOP her husband did not know the individuals arrested. She expressed apprehension that the Russia’s Intelligence (SVR) would try to use his death as propaganda.

U.S. intelligence authorities have not responded to inquiries about Tretyakov.

Editor’s note: This story was originally published on WTOP.com on July 9, 2010.