Gun-Toting police and federal agents at Atlanta's Summer Games are being joined in the fight against terrorism by a new security force - a vigilant public.
Since the bombing in Centennial Park, the groups charged with protecting the Olympic city are seeking public assistance in tracking down the culprit. They're also encouraging people to play a larger role in alerting authorities to other potential problems.
Behind the effort is a growing realization that despite intensive security measures, the United States is entering a new era of vulnerability to terrorism and must enlist its citizens in the war against it.
From the investigation of Unabomber suspect Theodore Kaczynski to the downing of TWA Flight 800, authorities are increasingly relying on "tips" gathered from telephone hot lines, the Internet, and other sources.
While experts say such leads rarely break cases, they note that the information is all part of the "intelligence" needed to build cases and prevent attacks.
"We'll end up doing a few more things on the prevention side" to stem terrorism in the future, says one security expert. But "we need to get the public more involved."
Public participation has played a key role in the investigation into who planted a crude pipe bomb near a concert stage in Centennial Park early Saturday morning.
More than 600 calls have flooded into an FBI hot line set up for the investigation, and the agency is asking anyone who took photographs or used a video camera in the area at the time to come forward.
In addition, more people are calling to report suspicious packages around the city, although none has turned up any explosive devices. As a result, investigators say they have significant leads as to who committed the crime. Using witness accounts, they are creating composite sketches and developing a psychological profile of the bomber.
"We're accepting information from anyone and anywhere," says FBI spokesman David Tubbs.
Still, the emphasis on public awareness highlights the delicate balance between informing citizens and contributing to a sense of hysteria. And it illustrates the difficult task of identifying which of an array of potential threats might be real.
In Atlanta, for example, the pipe bomb that exploded was preceded by a 911 call placed at a nearby pay telephone. The caller told a police operator that a bomb would explode in 30 minutes in Olympic Centennial Park. By the time that information was relayed to security personnel in the park the bomb had already exploded.
At the same time the bomb threat was received, a sharp-eyed security officer spotted the suspicious knapsack. Officials checked the contents and then began clearing people away from it. The parcel exploded 18 minutes after the phone call was made.
The delay in getting the 911 call to park security officials has raised questions about the speed of communications between Atlanta police headquarters and Olympic security officials. Had security officials in the park been aware of the telephoned bomb threat they might have taken more forceful action in clearing spectators away from the suspicious package.
Atlanta police officials defended their procedures for dealing with telephoned bomb threats. Typically, after the 911 operator relays a telephoned bomb threat to police, an officer is sent to the location of the telephone call, the bomb management squad is notified, and finally Olympic security officials. Those personnel were about to be told of the bomb when it exploded.
Part of the problem early Saturday was that the caller gave only a general location for the bomb - Centennial Park - a 21-acre landscape crowded with people, vendors, and large exhibitions. Moreover, Olympic security personnel have been responding to dozens of bomb threats each day.
"You investigate each one, you take them seriously, but you cannot notify the public every time," says Derick Hulme, an expert on terrorism and the Olympics. "There's simply too many people, and your potential for panic and the problems associated with that outweigh the potential benefits."
"You would hope they could get the message there faster, but even if they did, the park was packed and they would have been very lucky to stumble on that device," says Neil Livingstone, who heads a crisis management firm in Washington. "Short of bomb threats that go directly to buildings where people are inside, you usually have to go through different layers of security elsewhere and it takes time.''
Many experts say the blast could have been more devastating had it not been for the quick action of the officials who started to clear the area just before the blast.
"It seems to me that you can look at the bombing not as a failure of the security at the Olympics but as a success," Mr. Hulme says. "The bomb didn't go off at the Olympic Village; it didn't go off at the venues, it went off really in one of the only unsecured areas."
"I'm not sure what [Olympic security officials] can do to increase security, short of making Centennial Park a more restrictive venue," Mr. Livingstone says. "But you'll have thousands of people milling on the streets nearby who wouldn't want to wait for the lines of security, so you'd create another vulnerable site."
When Centennial Olympic Park reopens today, it will be with twice as many security officers, more surveillance cameras, random searches of bags, and a more watchful public.