Washington ? The CIA has stopped using contractors to interrogate prisoners and fired private security guards at the CIA’s now-shuttered secret overseas prisons, agency Director Leon Panetta said Thursday.

Panetta told agency employees in an e-mail that the guards will be replaced with CIA officers at the sites, which President Barack Obama ordered closed on his second day in office.

Terminating the private security guards who watched over the secret sites would save the agency $4 million, Panetta said. The CIA refused to provide details about the contract, including its total value and the company or companies that were fired.

The secret prisons are now empty, Panetta said, and the agency has not taken any new prisoners since he became director in February.

The CIA is now preparing plans for the prisons to be permanently shut down. An intelligence official said the facilities have to be cleaned of any potentially sensitive materials before they can be closed. The official spoke on condition of anonymity because he was not authorized to discuss the process.

The CIA, however, still has the authority to hold and interrogate prisoners for short periods. Panetta said they will be interrogated by agency employees, not private contractors, and then quickly handed over to the U.S. military, or to their home countries or countries that have legal claims on them.

Between 2002 and 2006, the CIA held and interrogated fewer than 100 prisoners, former CIA Director Michael Hayden told Congress last year. It used harsh interrogation methods on about a third of them. Three prisoners were subjected to waterboarding, a form of simulated drowning.

Hayden also confirmed to Congress that private contractors had been used to conduct interrogations, especially in the months immediately following the Sept. 11, 2001, terrorist attacks when the CIA did not have interrogators of its own.

National Intelligence Director Dennis Blair told the Senate Armed Services Committee in January that the CIA would only use its own cadre of trained interrogators to conduct interrogations.

Senate Intelligence Committee Chairwoman Sen. Dianne Feinstein, D-Calif., has been pushing for the formal abandonment of using contractors in interrogations.

An investigator for the Council of Europe, a human rights group, has alleged that 14 European nations colluded with U.S. intelligence to aid in the movement of 17 detainees who said they had been abducted by U.S. agents and secretly transferred to detention centers around the world. Some said they were sent to alleged secret facilities in countries including Poland, Romania, Egypt and Jordan, according to the investigator, Swiss senator Dick Marty.

Poland and Romania have vehemently denied the allegations, and most of the other EU countries mentioned by Marty have denied any wrongdoing.