The 79-year-old Hanssen was found unresponsive in his cell at a federal prison in Colorado and later pronounced dead, prison officials said. He is believed to have died of natural causes.

Robert Hanssen, a turncoat American spy whose leaks to Moscow the FBI dubbed “possibly the worst intelligence disaster in U.S. history,” was found dead in prison Monday.

Robert Hanssen, FBI agent who spied for Moscow, dies in prison at 79 He disclosed highly classified materials and betrayed U.S. assets -- including two who were later executed -- in one of the ...

Robert Hanssen, a former FBI agent who received more than $1.4 million for committing espionage on behalf of Moscow, died in prison, officials said.

Robert Hanssen, one of the most notorious spies in the history of the United States, was found dead in federal prison Monday morning.

Mr. Hanssen was sentenced to life in prison in 2002, bringing to a close one of the most lurid and damaging espionage cases in American history.

WASHINGTON, June 5 (Reuters) - Robert Hanssen, the former FBI agent turned spy whom the bureau describes as the most damaging in its history, was found dead in his prison cell on Monday, U.S ...

Robert Philip Hanssen, who received payments of $1.4 million in cash and diamonds for the information he gave the Soviet Union and Russia, has died, the Federal Bureau of Prisons announced Monday ...

Robert Philip Hanssen, who received payments of $1.4 million in cash and diamonds for the information he gave the Soviet Union and Russia, has died, the Federal Bureau of Prisons announced Monday ...

In 2001, Robert Philip Hanssen pleaded guilty to 15 counts of espionage and conspiracy in exchange for the government not seeking the death penalty.