Sen. Richard Shelby (search) is the target of an ongoing Justice Department investigation into the leaking of the contents of classified phone intercepts received the day before the Sept. 11, 2001, attacks, congressional sources told FOX News.

Justice Department officials briefed members of the Senate Select Committee on Intelligence (search) in closed session Thursday on Capitol Hill, naming the Alabama Republican as the target of the leak probe.

Law enforcement and congressional sources said the purpose of the briefing was to notify Congress of the department's intent to refer information collected to the Senate Select Committee on Ethics (search) for review.

Congressional sources told FOX News the ethics panel is now involved in the matter, though aides to the committee's bipartisan leaders, Republican Sen. George Voinovich of Ohio and Democratic Sen. Harry Reid of Nevada, declined to comment.

Virginia Davis, Shelby's spokeswoman, told FOX she had "no additional information" about the case. Davis declined to say whether Shelby's office had asked the Ethics Committee if it had received any information from Justice about the probe.

Davis sent FOX a copy of a statement from Shelby that the senator issued in January:

"My position on this issue is clear and well-known: At no time during my career as a United States senator and, more particularly, at no time during my service as chairman of the Senate Select Committee on Intelligence have I ever knowingly compromised classified information. To my knowledge, the same can be said about my staff. We have provided the investigation with our full cooperation in the past, and we will continue to do so."

Shelby served on the intelligence panel for eight years. Currently, he is chairman of the Senate Banking, Housing and Urban Affairs Committee (search).

Law enforcement sources said the Justice Department investigation remains "open" but the decision to refer the information collected so far to the Ethics Committee suggests the FBI may not have enough evidence to bring charges and is now leaving the matter up to the Senate.

The case involves the leaking of intercepted messages from Sept. 10, 2001. The National Security Agency intercepted the messages — "The match begins tomorrow" and "tomorrow is zero day" — suggesting an attack might occur the next day. The Arabic messages were not translated until Sept. 12.

The contents of the messages were revealed in closed session of a House-Senate panel investigating the Sept. 11 attacks by Air Force Lt. Gen. Michael V. Hayden, then-director of the National Security Agency.

FOX News' Jim Angle, Anna Stolley and Major Garrett contributed to this report.