"It was just a small piece, shaped like that," explained Frank Farrell, a wizened, 75-year-old retiree, gesturing to describe the strange object he saw while strolling the beach this morning.

"I couldn't tell if it was a cone or what," said Farrell, a former New York hotel operator who has lived on Florida's "Space Coast" for 16 years. "My smart brains were lost some years ago when I had a stroke."

What Farrell thinks he saw was a small chunk of the ill-fated Challenger space shuttle, which exploded 74 seconds after liftoff from nearby Cape Canaveral on Tuesday, killing the seven astronauts aboard.

Debris from the explosion rained into the Atlantic Ocean, some of it washing up to the gleaming, sandy shoreline for miles north and south of the Cape.

As this stunned community tries to return to normal, beachcombers have their eyes peeled for pieces of the shuttle that officials of the National Aeronautics and Space Administration hope will help solve the mystery of what caused the explosion.

So the discovery of a small chunk of material here, just behind Desperado's Restaurant, caused a minor stir among the scores of residents and visitors who strolled the beach on this spring-like day.

Actually, it wasn't Farrell, but an unidentified boy, who discovered the object and summoned police.

"It was fiberglass with lamination on it," said Steve Hunter, who operates a snack bar near where the object was found. "There have been jeeps driving up and down the beach and helicopters flying all over. I'm sure everybody's keeping an eye out."

Patrolman Michael Gombar of Cocoa Beach said residents have turned in "quite a few pieces" of the shuttle.

"People have been vigilant about it," he said. "It's a once-in-a-lifetime shot."

But as for the piece found this morning, Gombar said he doubted it was the real McCoy. "I thought it was a piece of slate," he said.

NASA and Coast Guard officials have focused the recovery mission along a 50- to 60-mile stretch of the Florida coast from New Smyrna Beach south to Vero Beach.

So far, about 1,600 pounds of debris has been recovered, according to NASA, much of it odd-shaped metal fragments and tiles from the shuttle's reentry heat shielding. Some large pieces, including one 30 feet by 5 feet, also have been recovered, and this afternoon searchers at sea reported finding a large piece of Challenger's fuselage and possibly part of its cockpit.

Some of those who roamed the beaches today told of witnessing the tragic liftoff.

"It was like an atomic explosion," said Dagmar Parker of Dodge City, Kan., who is vacationing here.

"You could see nothing was left," added her husband, Orlyn, a farmer and rancher. ". . . Pieces were falling out of the sky."

As seagulls lazily circled overhead, Maxine Marshall of Huntington, W. Va., recalled with a shudder that she and her husband saw the explosion from their car as they were driving toward the Cape.

"It was really beautiful until all of a sudden that blast or whatever," she said. "I just felt sick to my stomach."

Wayne Adaska, a civil engineer from Chicago attending a conference here, witnessed the explosion from a commercial airliner about to land.

"It definitely will be an historical event to tell my kids back home," he said.

The scene today was placid along the coast, which is lined with boxy hotels and condominiums and shabby snack shops. Dozens of shrimp boats were anchored offshore. Elderly couples held hands as they walked along the beach. Two young men tossed a Frisbee. A young woman played in the sand with her daughter. And several older women sat on beach chairs, knitting away.

It is a friendly place and people generally nod hello as they pass.

Farther south, near Patrick Air Force Base, Jack and Dorothy Sharkey, a retired couple from Chestertown, N.Y., spent the day fishing from the shore.

"We saw a tile up the way and thought it was part of the shuttle," Dorothy Sharkey said as she tended three poles stuck in the sand. "But someone said, 'No, that's a bathroom tile.' "

George Doane, a retired nursing-home operator from Goshen, N.Y., who was also fishing there, said he had watched the shuttle launch from his parked car. "When it went up I was thinking about that schoolteacher," Christa McAuliffe, said Doane. "I thought to myself, now she's in her glory. Then, suddenly, boom."

By midafternoon today a chilly breeze began blowing clouds in from the ocean. Near Satellite Beach, Margaret and Tom Grassley of Hamilton, Ontario, buttoned their sweaters as they took one last stroll along the shore before their trip home to Canada.

Margaret Grassley was scouring the beach but she was not looking for shuttle debris. "Look at these," she said, taking a dozen mottled seashells from her pocket.

But Tom Grassley was more interested in talking about Challenger.

"It went up just like a Roman candle," he said. "This is the first time we've been down to the shore since . . . . We've seen on TV how people have found lots of pieces. If there's anything green on them, you're not supposed to touch it."

Margaret Grassley opened her hand again to display the pretty seashells.

"This is my favorite one," she said, indicating a large brown shell. "I think they'll look lovely in a fishbowl."