Widespread Plot Doubted

Federal prosecutors in the Oklahoma City bombing case are preparing to charge that the deadliest terrorist act in American history was not the widespread, well-organized conspiracy that was first suspected, but the work of only two or three disgruntled former soldiers.

The indictments, which must be brought by Friday under federal speedy-trial regulations, are expected to charge the only two suspects in custody, Timothy McVeigh and Terry Nichols, with the truck-bomb explosion that ripped apart the Alfred P. Murrah Federal Building, killing 167 people, including 15 children in a day-care center.

Michael Fortier, a third member of the same infantry unit from Fort Riley, Kan., has been negotiating with federal authorities for leniency in exchange for his testimony.

It now appears possible that Fortier, who has not yet appeared before the federal grand jury and thus remains a potential defendant, may have played a larger role than first believed, according to participants in the investigation and to the defense and an independent reconstruction of the events.

But investigators, who have discovered a host of details about the two suspects in custody, are intrigued by phone calls McVeigh made shortly before the bombing, a time when both the defense and investigators now believe that McVeigh and Nichols had a falling out.