Reid sent a letter to CIA Director John O. Brennan late Wednesday stating that he has asked the Senate Sergeant at Arms to review the computers used by committee investigators and asked that he grant proper security clearances and access to the computers. As part of the committee probe, the CIA set up a secret facility in Northern Virginia with computers where investigators were promised unfettered access to millions of documents describing the interrogation program.
Senate Sergeant at Arms Terrance W. Gainer serves as the chamber's top law enforcement official and has oversight of the U.S. Capitol Police.
Aides said Thursday that Reid had raised concerns about possible interference with the investigation in recent months during his regular briefings with Brennan, a fact he also mentioned in his letter.
In his message to Brennan, Reid rejected as "patently absurd" suggestions that committee staffers improperly accessed classified information about the agency and the interrogation program. "To my knowledge, the CIA has produced no evidence to support its claims that Senate committee staff who have no technical training somehow hacked into the CIA's highly secure classified networks," Reid said.
As part of the dispute, CIA officials have referred the matter to the Justice Department.
In a separate letter sent Wednesday, Reid asked Attorney General Eric H. Holder Jr. to "carefully examine" the accusations leveled by the Senate Intelligence Committee and the CIA against each other.
"The CIA's decision to access the resources and work product of the legislative branch without permission is absolutely indefensible, regardless of the context," Reid wrote to Holder. "This action has serious separation of powers implications. It is immaterial whether this action was taken in response to concerns about the Committee's possession of a disputed document; this stands as a categorically different and more serious breach."
Holder told reporters Wednesday that the Justice Department is reviewing the CIA’s referral of the case, but would not say whether the department has decided to investigate the matter.
Feinstein has said that she expects her committee will vote to declassify their 6,000-page report on the interrogation program by the end of the month. The investigation has been underway since 2009 and is believed to have cost taxpayers at least $50 million.