DoJ OIG, May 08: A Review of the FBI's Involvement in and Observations of Detainee Interrogations in Guantanamo Bay, Afghanistan and Iraq
....Our report found that after FBI agents in GTMO and other military zones were confronted with interrogators from other agencies who used more aggressive interrogation techniques than the techniques that the FBI had employed successfully for many years, the FBI decided that it would not participate in joint interrogations of detainees with other agencies in which techniques not allowed by the FBI were used....
Note the careful verbiage. Complete 438 page report (with redactions) available at the link.