A former FBI agent who took more than £1.1 million in cash and diamonds to trade secrets with Russia has died in prison.
Robert Hanssen, 79, was found unresponsive in his cell at a federal prison in Colorado on Monday and later pronounced dead, officials said.
He had been serving a sentence of life in prison without possibility of parole since 2002, after pleading guilty to 15 counts of espionage and other charges.
Hanssen had joined the FBI in 1976 and began selling classified information to the Soviet Union in 1985.
By the time of his arrest in 2001, he had received over £1.1 million in cash, bank funds and diamonds in exchange for compromising numerous human sources, intelligence techniques and classified US documents.
Using the alias Ramon Garcia, he passed some 6,000 documents and 26 computer disks to his handlers, authorities said.
Officials also believe he tipped off Moscow to a secret tunnel the Americans built under the Soviet Embassy in Washington for eavesdropping.
FBI investigators had worked for years to identify the spy within their ranks but did not arrest Hanssen until February 2001. Some 300 personnel had worked on the investigation, the FBI said.
An arrest team took Hanssen into custody after catching him making a “dead drop” of classified materials in a park in suburban Virginia, according to the intelligence agency.
Hanssen had been serving his life sentence in a maximum security facility in Colorado.
The Bureau of Prisons did not provide a cause of death.
