Law enforcement officials across the country remained on high alert today for potential attacks on the New Year's Eve holiday.
National security officials in Washington, from the Department of Homeland Security to the FBI, focused their attention on New York City and Times Square, where local law enforcement finalized preparations for the annual New Year's Eve bash.
For now, however, there is no credible, specific terror threat timed to the celebration, federal and local intelligence and counterterror officials told ABC News.
"We have no specific threats against the city on New Year's Eve," New York City's Police Commissioner Ray Kelly said. "Anytime large numbers of people come together, we put in our counterterrorism overlay. We have other events going on: We have a four-mile run in Central Park at midnight; a fireworks display at Prospect Park in Brooklyn; fireworks by the Statue of Liberty. ... So it's not just Times Square.
"But I can assure you we looked at all of these events closely. We will have several thousand police officers deployed. ... We have every indication that it will be a safe and happy event. "
The New York Police Department put the finishing touches Thursday on the "ring of steel" it uses to protect revelers: a security screen consisting of 17-plus miles of barricades; entrance point searches; video feeds; and uniformed officers spaced every few yards.
"I can tell you that we have more cameras focused on this area now, we're monitoring more cameras than we've ever done in the past," said Kelly as he showed an ABC News team around Times Square.
There will also be numerous security measures not quite so apparent to the untrained eye that include chemical sniffers, biological sensors and handheld radiation wands and pagers.
A few fun facts for revelers to contemplate as they stand with noisemakers, hats and masks, bodies pressed against barricades, huddled against the cold and in some cases perhaps with their knees held close together to prevent nature's urges from getting the best of them:
The ball weighs 6 tons and is 12 feet in diameter.
It begins its 60-second count to 2011 from a stanchion 400 feet above Times Square.
The ball consists of 32,000 lightbulbs.
90,690 feet of aluminum and wooden police horses have fenced the area in years past.
That 17.18 mile-protective fence weighed in, when last tallied by ABC News, at more than 355,000 pounds.
"When you come here, the energy is something that you've never experienced before and that's feeling of community," said Jeffrey Strauss of Countdown Entertainment, which runs the New Year's Eve celebration in Times Square. "It's unique."
"When you're watching Times Square, you're seeing people kissing and celebrating and having fun. That's what New Year's is all about," Strauss said.
The city will not make an official crowd estimate. But in years past the estimates have ranged up to a million people. And worldwide electronic viewership has been estimated at a billion or more, Strauss said.
Officials charged with security are keenly aware of both last year's attempted Christmas airplane bomb attempt, and last spring's attempted Times Square bombing. They are deeply concerned that a stray backpack or plastic bottle containing a bomb, or bomb ingredients, could be slipped inside the police lines.
To keep partygoers safe, authorities have issued their annual reminders:
Backpacks and large bags are prohibited.
Alcoholic beverages are prohibited.
Property may not be abandoned at checkpoints.
Attendees who leave before the ball drops will not be able to return to their original viewing areas.
To enforce these rules and monitor for suspicious activity, there will be thousands of uniformed and plainclothes officers assigned to security tonight, including officers armed with radiation detectors and others handling bomb sniffing dogs. Snipers and heavy weapons teams will also be on hand.
Commissioner Kelly was asked if this was the most secure Times Square had ever been.
"Well, I certainly hope so," he laughed.
Outside of Times Square, special roving units will have citywide duty, ready to move to any other location deemed in need of a critical response. And inside of the frozen zone there will also be "flying squads" of detectives and specialists ready to swoop in on any suspected terrorist, nutcase or common criminal.
In years past, there have been false alarms, including a threat passed on by Canadian authorities to the FBI that poison gas was hidden inside the pyrotechnics that would help ring in the New Year when they burst from the roof of Number One Times Square.
Never mind that fireworks 395 feet above street level would make a lousy mechanism for dispersing gas; a team of New York City cops climbed up, took samples, determined there was no threat and the revelries went on.
As the city slept in on Jan. 1, 2010, more than 150 members of the Dept. of Sanitation swept up an estimated 46.96 tons of confetti and debris in just a few hours. Officials estimated that cleanup cost was $54,000 in 2009.