Richard Jewell, 33, a former deputy sheriff, was questioned at his Atlanta home last night by FBI agents who said later they expected to arrest "a suspect" today.
FBI agents said Mr Jewell - who had left various police jobs "on bad terms" and was out of work before getting the job as a security man in Atlanta - fitted the profile of the man believed to have planted the bomb which killed a Georgia mother and was blamed for the heart-attack death of a Turkish newsman. More than 100 people were wounded.
The FBI believes Mr Jewell, described as "frustrated" over his recent personal life, left the crude pipe-bomb in Centennial Park, walked to a payphone 200 yards away to give a bomb warning, then returned to a safe distance from the blast to act as a hero. He may have been hoping this would get him a future police job, FBI agents said.
After the bombing, Mr Jewell was widely interviewed by the media. He billed himself as a modest hero and was treated as something of a celebrity.
Last night, after being questioned, and still wearing the white anorak of this private security agency, he denied he was the bomber.
The NBC television network, which has a strong journalistic presence here because of its exclusive rights to the games, said the FBI had matched Mr Jewell's voice to that of a man who phoned the bomb warning which said "there is a bomb in Centennial Park. You have 30 minutes" before hanging up.
In his media interviews after the explosion, Mr Jewell said: "At first it was a calm urgency of 'this is what we've got to do'. It's almost like you're looking at a computer screen. Your brain pulls up an automatic list of what you've got to do.
"It knocked me to the ground, to my hands and knees. As I was getting up, I looked to my right and I saw two of the troopers still flying through the air. I ran down in that direction because some of those guys are my friends."
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