The Bureau office in Anchorage, Alaska, released a statement saying the Keyes told authorities he killed two people in Washington sometime during 2005 and 2006 and murdered a Washington couple between 2001 and 2005.
Officials have released no specific details.
The FBI says Keyes, who lived in Washington most of his life, is believed to have committed multiple kidnappings and murders across the country between 2001 and March 2012.
