The Justice Department appears to be nearly done with fallen lobbyist Jack Abramoff, but observers say that should provide little comfort for other figures in the sprawling corruption probe.

Prosecutors and Abramoff’s attorneys filed a joint motion Monday asking the U.S. District Court for the District of Columbia to sentence Abramoff in September on the three felony counts that he pleaded to in January 2006: conspiracy, honest services fraud and tax evasion.

Abramoff, like many of his co-conspirators who have also pleaded guilty, regularly had his sentencing delayed while he cooperated with the government’s investigation.

But the Justice Department’s decision to get on with Abramoff’s sentencing probably has no bearing on the fortunes of the other figures in the case, sources familiar with the scandal said, and certainly does not indicate that the investigation is waning.

Stan Brand, a noted white- collar defense attorney, said “it may be that they have finally exhausted him as a witness,” given the fact that he has been cooperating with investigators for more than two years. Brand said Abramoff is already serving a five-and-a-half year sentence for fraud relating to his ownership of Florida-based SunCruz Casinos, and the Justice Department may be attempting to get his sentencing for the conspiracy under way so it can avoid adding additional jail time.

The joint motion states that “While the government anticipates that Mr. Abramoff’s cooperation in the form of possible testimony will continue for the foreseeable future, the parties believe that they are in a position to inform the court about the full scope of his misconduct and cooperation.” Therefore, “sentencing in the near future in this case is appropriate.” The motion suggests a September sentencing date.

Brand said federal investigators appear to have “moved beyond Abramoff … they are into a whole other layer of people who could supply them with more information even than he could.”

Several sources close to the investigation said the Abramoff sentencing would have no effect on the remainder of the case because the government now has many more sources of evidence than it did when Abramoff pleaded guilty. And while he was central to the conspiracy to trade favors for legislative assistance, many of the specifics of gift exchanges were carried out by his co-workers, many of whom are now cooperating with the government.

In this sense, Abramoff may be further from the specific, indictable offenses than some of his colleagues, and the fact that he appears to have told the department all that he can does not suggest that there is no more useable information for prosecutors.

Other figures in the case who have continued to have their sentencing delayed are Michael Scanlon, a former spokesman for ex-Rep. Tom DeLay (R-Texas) who set up a scam with Abramoff to over bill Indian tribes; Tony Rudy, a DeLay staffer who left the Hill to join Abramoff’s lobbying team; and former Transportation and Infrastructure Committee staffer Mark Zachares, who took cash and favors from Abramoff in exchange for helping Abramoff’s clients.

Earlier this month, John Albaugh, a former staffer to then-Rep. Ernest Istook (R-Okla.), also pleaded guilty to accepting favors in exchange for providing assistance to Abramoff’s clients.

Several major figures in the Abramoff case have never faced charges, including Ed Buckham, a former DeLay chief of staff who launched the Alexander Strategy Group after leaving the Hill and ultimately hired Rudy. A federal grand jury subpoenaed the House for Buckham’s e-mails and payroll records in September. Albaugh’s guilty plea indicated that Kevin Ring, a former staffer to Rep. John Doolittle (R-Calif.), had been his conduit to Abramoff, but Ring was not named in the plea and has not been charged in the case.

The FBI has raided Doolittle’s home, but neither he, Istook nor Delay has been charged in the case.

Several sources said the Albaugh indictment implied that the investigation is expanding, not shutting down, by presenting the first information about criminal activity in Istook’s office. Istook did not return telephone calls requesting comment.

The Justice Department and Scanlon’s attorney issued a joint motion last week asking to again delay his next status hearing, which was scheduled for Friday. The parties have asked for a delay of at least 90 days. Zachares’ next status conference is scheduled for Sept. 18.

Meanwhile, the House Oversight and Government Reform Committee continues to investigate Abramoff’s dealings with the White House, scheduling a Thursday hearing to vote on a draft report offering evidence of about 150 contacts between White House officials and Abramoff’s team, down from the 480 that had previously been reported.