Upping the ante in the U.S. attorneys probe, Senate Judiciary Chairman Patrick Leahy (D-Vt.) issued a subpoena on Wednesday for e-mails written by presidential adviser Karl Rove and thought to be in the possession of embattled Attorney General Alberto Gonzales.

It is the first subpoena actually issued by the Senate committee in its investigation into the firing of eight U.S. attorneys and may signify that more are on the way. The committee has several times voted to give Leahy the authority to subpoena witnesses — including Rove — and documents.

The House Judiciary Committee has subpoenaed various e-mails and documents in the wide-ranging probe. The committee will hear this morning from former Deputy Attorney General James Comey, after issuing a subpoena to him earlier in the week.

On Wednesday, Leahy demanded the Rove e-mails, written either from an official White House account or a political e-mail address, by May 15 or for Gonzales himself to appear before the committee and explain their whereabouts.

Democrats believe Gonzales or the Justice Department may have relevant e-mails because they were commandeered by special counsel Patrick Fitzgerald as part of the Valerie Plame leak investigation.

“We have received the subpoena and are reviewing it,” Justice Department spokesman Dean Boyd responded Wednesday.

Boyd added that the department has turned over “6,000 pages of documents” and voluntarily allowed “hours of interviews” with senior Justice officials and testimony by Gonzales.

But in a May 2 letter to Gonzales, Leahy decried those records as “selective and incomplete.”

“Many documents have been withheld or redacted without any legal basis being set forth,” Leahy wrote. “The Department continues to insist on providing information within only a highly limited scope inconsistent with the Committee’s inquiry and over the Committee’s objection.”

In a separate May 2 letter to Gonzales, a bipartisan group of Senators — including Judiciary ranking member Arlen Specter (R-Pa.) and Sen. Jeff Sessions (R-Ala.) — also requested that Gonzales turn over a confidential March 2006 memo regarding personnel decisions. In the memo, Gonzales delegated firing and hiring decisions for political employees at Justice to two former top aides, then-Chief of Staff Kyle Sampson and ex-White House liaison Monica Goodling, both of whom have resigned as the U.S. attorneys scandal unfolded.

In pursuing the Rove e-mails, Democrats are reacting to reports that White House aides might have used Republican National Committee e-mail accounts to conduct official business. The White House and RNC have said those e-mails may be lost.

But in an April 13 Associated Press story, Rove attorney Robert Luskin contended that Rove thought the e-mails were being archived. Luskin said that Fitzgerald had subpoenaed and copied Rove’s e-mails from his laptop, home computer and personal communications devices. This is why Democrats believe the Justice Department may have them.