The FBI office in Birmingham launched an immediate investigation. In a 1965 memo to J. Edgar Hoover, FBI agents named four men as primary suspects for the bombing - Thomas Blanton, Robert Chambliss, Bobby Frank Cherry, and Herman Cash. All four men were members of the Ku Klux Klan. The investigation ended in 1968 with no indictments. According to the FBI, although they had identified the four suspects, witnesses were reluctant to talk and physical evidence was lacking. In 1971, Alabama Attorney General Bill Baxley reopened the case, requesting evidence from the FBI and building trust with witnesses who had been reluctant to testify. Investigators discovered that, while the FBI had accumulated evidence against the bombers, under orders from Hoover they had not disclosed the evidence to county prosecutors.