Darryl Littlejohn, a 41-year-old ex-con, was considered a potential suspect in the slaying of Imette St. Guillen, sources said last night after cops hauled away bags of possible evidence from The Falls bar.

The bouncer was seen speaking to St. Guillen in the bar before she disappeared about 4 a.m. on Feb. 25 - and cell phone records place the Queens man in Brooklyn about 6 a.m., sources said.

The 24-year-old criminology student's body was found in Brooklyn, off the Belt Parkway, about 15 hours later, after an anonymous male tipster called 911 from a pay phone at a nearby diner.

Hours before he was being questioned at Brooklyn's 75th Precinct stationhouse, Littlejohn called a Daily News reporter yesterday morning to say he had nothing to do with the horrible crime. He accused cops of harassing him.

The potential breakthrough came as detectives swooped into The Falls as they pursued a theory that St. Guillen - who was alone and had been drinking before she was killed - was snatched quickly after leaving the hot spot and pulled into another part of the building.

Cops, some in protective white jumpsuits, searched 218 Lafayette St. yesterday, shutting the first-floor bar where the vivacious John Jay College of Criminal Justice grad student was last seen. They meticulously gathered bags of hair and fiber evidence as they examined the basement, roof and second-floor offices - which have an inner door and stairway leading to the bar, said former vice presidential candidate Geraldine Ferraro, whose family owns the building.

"They went into the basement, they went on the roof, they went upstairs to the second floor. We allowed them total access to anything that they wanted to see," Ferraro told The News last night.

Offices on the second floor of the building are used by a variety of businesses connected to her husband, John Zaccaro, and by a charity group that counts Ferraro among its supporters.

Investigators were looking into whether the inner doorway - which is kept locked and alarmed - and staircase were somehow used by the killer after snatching the beautiful and brainy Boston native, sources said.

St. Guillen was raped, tortured and suffocated - and dumped in a secluded area in East New York. Her face had been wrapped in tape and her naked body was rolled in a floral-patterned blanket.

Cops returned to The Falls because they have no evidence St. Guillen was ever seen anywhere else after leaving there, sources said.

In addition to Littlejohn, who has a history of robbery and drug raps, cops have shown intense interest in at least one other man who works at the bar, sources said.

Cops asked that man to disrobe for them, to prove he had no scratches on him. He did so and had no marks, the sources added. St. Guillen had skin under her fingernails.

About 10 cops, some wearing white plastic jumpsuits used in sensitive evidence collection, walked into the Lafayette St. building yesterday carrying a tripod and plastic spray bottles at one point.

They later emerged with cardboard file boxes containing Manila envelopes and papers bags - including at least one labeled "hairs and fibers."

Crime scene investigators finally left shortly before 9 p.m., carrying a clear plastic bag that appeared to contain a thick off-white fabric.

The search of the bar building came a day .after St. Guillen's funeral in her native Boston. Her slaying, which has shaken New York and garnered national attention, has sparked a $42,000 reward fund.

Meanwhile, cops were investigating whether a decomposed corpse found yesterday in a plastic bag a mile from the Belt Parkway in eastern Queens was somehow linked to the slaying. While the body's age, gender and race have not been determined officially, cops believe it was a black teenage girl.

Cops swarmed out to a desolate wetland near Brookville and Rockaway Blvds., just east of Kennedy Airport, about 10:10 a.m. after a man reported finding the body.

Sources said the gruesome discovery was made by an off-duty Rockville Centre, L.I., cop looking for a friend, Thomas Fasciglione, 50, of East Rockaway, L.I., who disappeared more than a month ago. In a sad irony, Fasciglione's body washed ashore near some docks in East Rockaway about half an hour later, cops said.