The Government's investigation into who leaked the identity of CIA undercover agent Valerie Plame may be taking a step forward. A fourth prosecutor has been assigned to the case and the FBI has said administration officials may be called to a grand jury.

On Monday, the Senate minority leader and the ranking Democrat on the Armed Services Committee sent a letter to Attorney General John D. Ashcroft demanding more information about the probe. "We request that you provide us with an overall status of the investigation, including the number of people the Justice Department has interviewed, the number of briefings you have received, the general types of information you are briefed on, what conditions you have placed on the scope of these briefings to ensure the independence of this investigation, and whether you have discussed this case with senior administration officials outside the Justice Department," wrote the senators, Thomas A. Daschle (S.D.) and Carl M. Levin (Mich.).

The senators said that it is an apparent conflict of interest for Ashcroft to be briefed on the subject, and again requested a special counsel to prosecute the case, which Ashcroft has so far opposed.

There's lots more detail in this article, so read the whole thing. Our Valerie Plame coverage is accessible here.