An aide to Senate Majority Leader Bill Frist (search) has been put on leave during an investigation into how Republicans gained access to Democratic memos concerning opposition to President Bush's judicial nominees.

Manuel Miranda, who works for the Tennessee Republican on judicial nominations, is on leave pending the outcome of the inquiry by the Senate sergeant-at-arms (search), Frist spokesman Nick Smith said Tuesday. In the matter under investigation, Democratic memos stored on a computer server shared by Judiciary Committee members ended up in GOP hands.

Miranda told The Knoxville News-Sentinel that investigators were looking at work he performed for the Judiciary Committee before he joined Frist's office. "There was no stealing," he said. "No systematic surveillance. I never forwarded these memos -- period."

Asked about the investigation Tuesday, Frist refused to talk about it.

Senate Judiciary Chairman Orrin Hatch, R-Utah, began the investigation in November after Sens. Dick Durbin, D-Ill., and Edward Kennedy, D-Mass., protested what they said was the theft of the memos from their servers. The memos, concerning political strategy on blocking confirmation of several of President Bush's judicial nominations, were obtained and reported on by The Wall Street Journal and The Washington Times.

Republicans and Democrats on the committee got separate servers during the just-completed year-end recess, officials said.

Conservatives have talked up the memos as proof the Democrats colluded with outside liberal groups in their choices of which Bush appellate nominees to block.

The memos also show, conservatives contend, that Hispanic lawyer Miguel Estrada (search) was blocked largely for two reasons:

--Confirmation would have put him in line for a Supreme Court nomination, and Democrats did not want a Republican president to appoint the first Latino to that court.

--Democrats wanted to keep conservative nominees off the 6th U.S. Circuit Court of Appeals until after the University of Michigan affirmative action case (search) was decided.

Hatch, the Judiciary chairman, placed an aide on leave late last year for improperly obtaining data from the computer networks of two Democratic senators. That aide, who has not been identified, has since left government work, officials said.

The leak of the messages "shouldn't have happened. I'd be the first to admit that it shouldn't have happened, and I'm upset that it did," Hatch said Tuesday after being criticized by conservatives for going along with the investigation. Hatch said he hoped to make the final report public.

Senate Sergeant-at-Arms William Pickle has been working with the Secret Service and outside investigators since November to try and determine how the Democratic memos got to Republicans. A report is expected to go to Hatch's Judiciary Committee in about two weeks, officials said.

Pickle will brief Frist and Senate Democratic leader Tom Daschle of South Dakota privately this week. Hatch said he and senior Judiciary Democrat Patrick Leahy of Vermont already have received preliminary briefings.

Democrats have used the threat of a filibuster to block six U.S. Appeals Court nominees this congressional term: Estrada, Mississippi judge Charles Pickering, Alabama Attorney General William Pryor, Texas judge Priscilla Owen and California judges Carolyn Kuhl and Janice Rogers Brown.

Estrada had his nomination withdrawn last year. Bush gave Pickering a temporary appointment to the 5th U.S. Circuit Court of Appeals this month.