WASHINGTON - The FBI is investigating the alleged unauthorized removal of classified documents from a CIA facility by Senate Intelligence Committee staff members who prepared a study of the agency's use of harsh interrogation techniques on terrorism suspects in secret overseas detention centers.

WASHINGTON � The FBI is investigating the alleged unauthorized removal of classified documents from a CIA facility by Senate Intelligence Committee staff members who prepared a study of the agency�s use of harsh interrogation techniques on terrorism suspects in secret overseas detention centers.

The FBI�s involvement takes to a new level an extraordinary behind-the-scenes battle over the report that has plunged relations between the agency and its congressional overseers to their iciest in decades. The dispute also has intensified uncertainty about how much of the committee�s four-year-long study will ever be made public.

The CIA general counsel�s office asked the Justice Department for a criminal investigation into the removal last fall of classified documents from a high-security electronic reading room that committee staff members were required to use to review top-secret emails and other materials, people familiar with the issue said. The existence of the referral was first reported online Thursday afternoon by Time magazine.

The matter is now with the FBI, said one federal official. Like all of those who spoke to McClatchy, the federal official requested anonymity.

The request by the CIA general counsel is one of two criminal referrals sent to the Justice Department in connection with the committee�s 6,300-page report, which remains shelved nearly 15 months after the panel voted to approve its final draft, people familiar with the case say.

The second was made by CIA Inspector General David Buckley, they said. It relates to monitoring by the agency of computers that the committee staff members used in the reading room inside a secret CIA facility in northern Virginia, they said.

It was unclear when the referrals were made, when the FBI became involved or whether its investigation also includes the computer monitoring.

The FBI and CIA declined to comment. The committee referred calls to the Justice Department, which also declined to comment.