FBI agents repeatedly warned military interrogators at the U.S. prison camp at Guantanamo Bay that their aggressive methods were legally risky and also likely to be ineffective, according to FBI memos made public Thursday.

A senior officer at the prison for terror suspects also "blatantly misled" his superiors at the Pentagon into thinking that the FBI had endorsed the "aggressive and controversial interrogation plan" for one detainee, according to one of the 54 memos released by the American Civil Liberties Union.

The memos had been previously released, but in more heavily censored form, as part of a lawsuit by the ACLU under the federal Freedom of Information Act.

Agents on temporary assignment at the U.S. Navy facility in Cuba brought their concerns to the prison's commander, Maj. Gen. Geoffrey Miller, and laid them out in detailed messages to top bureau officials at FBI headquarters in Washington.

One memo from May 2003 describes tension between the FBI agents and their military counterparts over "aggressive interrogation tactics in GTMO which are of questionable effectiveness and subject to uncertain interpretation based on law and regulation."

A military investigation into FBI reports of prisoner abuse at Guantanamo recommended that Miller be reprimanded for failing to oversee the interrogation of a high-value detainee, which was found to have been abusive. But a top general rejected the recommendation. Miller recently requested early retirement.