FBI (search) agents working overseas in Iraq (search) and elsewhere did not participate in any abusive interrogation of prisoners or witness mistreatment, FBI Director Robert Mueller said Thursday.

Bureau guidelines prohibit agents from taking part in interrogations that involve force, threat of force or coercion, Mueller said. Agents are instructed to refuse to participate in any interviews they believe violate those FBI standards.

If agents see abuses, they are expected to report them up the chain of command, Mueller told the Senate Judiciary Committee.

But interviews with FBI agents working in the Iraq's Abu Ghraib prison (search) between October and December 2003 found that none saw or participated in any of the abuses of Iraqi detainees that are now the subject of military and Justice Department investigations, Mueller said.

"None of them witnessed abuses such as we have seen," he said.

Mueller said those guidelines apply in the United States and abroad. The CIA (search) and Defense Department, he added, have their own guidelines.

"My understanding is that there are standards that have been established by others, legally, that may well be different from the FBI standards," the director said. "And if that were the case, and they were a departure from the FBI standards, we were not to participate."

Mueller also said the FBI was not yet involved in any investigations of handling of prisoners in Iraq, Afghanistan or the U.S. naval base at Guantanamo Bay (search), Cuba. He confirmed that the CIA inspector general has referred cases for possible criminal prosecution to the Justice Department.