NEW YORK (AP) _ Moody's Investors Service, the nation's oldest credit-rating agency, is overhauling its management in a companywide shakeup that could include layoffs, The Wall Street Journal reported today.

The departures of several high-ranking Moody's officials, including the retirement last week of company president John Bohn, marked the beginning of the broad upheaval, the Journal said.

A Moody's spokesman did not immediately return a phone call today.

The changes come amid an investigation by the Justice Department into whether Moody's may have pressured bond issuers to hire it or face negative comments or lower ratings on their securities.

Among the reported changes at Moody's is a new way for handling bond rating assignments.

Bohn was succeeded last week by William O. Dwyer, who came out of retirement to take the job and has begun to implement the findings of an internal management report, the Journal said.

Moody's already has replaced its senior management team. In addition, its public finance department, which rates municipal bonds, will no longer be a stand-alone unit and will now report directly to the company president.

The department, a focus of the Justice Department investigation, will be part of a larger group that also rates corporate debt.

Thomas McGuire, who headed the corporate ratings department, resigned in the shakeup, the Journal reported, citing unidentified sources. Another official, public finance head Daniel Heimowitz, is expected to announce his resignation.

New York-based Moody's is owned by Dun & Bradstreet Corp. It and Standard & Poor's are the dominant firms in the business of evaluating the creditworthiness of bonds and other securities sold by government agencies and corporations.