CHARLESTON, W.Va. (AP) — U.S. Sen. Robert C. Byrd obtained secret FBI documents about the civil rights movement that were leaked by the CIA and triggered an angry confrontation between the two agencies in the 1960s, according to newly released FBI records.

Byrd, who died in June 2010 at age 92, had sought the FBI intelligence while suspecting that communists and subversives were guiding the civil rights cause, the records show. Decades before he became history's longest-serving member of Congress, or gained the title "King of Pork" for sending federal funds to West Virginia, the Democrat had stalled and voted against major civil rights legislation in the mid-1960s. He also belonged to the Ku Klux Klan while a young man in the 1940s, and the FBI cited that membership while weighing his requests for classified information, the records show.

"He eventually had a change of heart about a lot of that stuff," said Ray Smock, a former historian for Congress who now oversees Byrd's archives. Smock said Byrd's hardline belief in law and order played a role in his view of the civil rights movement. Byrd also repeatedly called his time with the hate group a serious mistake, Smock noted.