WASHINGTON  The Justice Department revealed on Friday that its internal ethics office is investigating the department’s legal approval of waterboarding of Al Qaeda suspects by the Central Intelligence Agency and is likely to make public an unclassified version of its report.

The disclosure by H. Marshall Jarrett, head of the department’s Office of Professional Responsibility, was the first public acknowledgment of an internal review of the series of legal memorandums the department has issued since 2002 authorizing waterboarding and other harsh interrogation methods.

His report could become the first public accounting for legal advice that endorsed methods widely denounced by human rights groups and legal authorities as torture. Mr. Jarrett’s office can refer matters for criminal prosecution, but legal experts said the likely outcome was a public critique of the legal opinions on interrogation, conceivably including reprimands for some current or former Justice Department attorneys who drafted them.

The disclosure came as a team of prosecutors and F.B.I. agents are conducting a criminal investigation of the C.I.A.’s destruction in 2005 of videotapes of harsh interrogations of two Al Qaeda suspects, both of whom were subjected to waterboarding. The technique, which has been used since the Inquisition, involves water poured into the nose and mouth to create a feeling of drowning. Congress has passed a ban on all coercive interrogations, but President Bush has said he will veto it.