Updated 12:31 a.m., Sept. 10, 2011
NEW YORK (CBSNewYork) -- Just two days before the 10th anniversary, New York City is on high alert.
Federal and local authorities have beefed up security after receiving intelligence about a credible threat. The alleged plot by al Qaeda involves detonating car bombs on bridges and in tunnels in New York and Washington D.C. to coincide with the anniversary of 9/11.
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Chopper 2 HD got a look at the NYPD in action on Friday -- police cruisers and orange cones marked one checkpoint on the George Washington Bridge. On the West Side Highway, at one of the many checkpoints, police were stopping drivers and searching vehicles, specifically vans and trucks. There is also a threat to bridges and tunnels.
Security was equally tight at Penn Station, where armed guards were keeping watch over travelers as Transportation Security Administration agents performed random bag checks, swiping packs for gunpowder.
The crossroads of the world came to a grinding halt at various times Friday because for police Times Square has become the ground zero of the latest terror threat. Sources told CBS 2's Marcia Kramer that another attempt to explode a bomb there is a key concern, and the intelligence suggests it could be a dirty bomb.
Based on informant information authorities are looking for three suspects. One is believed to be an American citizen. Two others apparently have U.S. travel documents.
Some of the information on the latest threat could be coming from Younis al-Mauritani, the man hand-picked by Osama bin Laden to develop terror targets in the United States. He's a "most wanted list" senior al Qaeda operative who was arrested in Pakistan last week with his computer, BlackBerry and other tools.
"Remember, an awful lot of the security we have you don't see," Mayor Michael Bloomberg said. "I'm satisfied that Commissioner Kelly has deployed all of our resources doing everything that we should be doing."
"Terrorism is theater and this is the stage," NYPD Commissioner Ray Kelly said. "This is right now probably the world's biggest stage. "
There was a lot of security you could see Friday in the Big Apple, especially in Times Square, because, as sources told Kramer, the intelligence includes information that al Qaeda wants to finish the job that started with Faisal Shahzad's failed car bomb attempt in May 2010.
Top security officials told Kramer this is the al Qaeda way. Their 1993 attempt to topple the World Trade Center failed, so they came back again on 9/11. Shahzad's car bomb fizzled, so now they want to try again.
But that's only half of the problem. Officials are worried that this time it could be a dirty bomb.
"We have to think about a dirty bomb, where you take radiological material and mix it with conventional explosives," Kelly said.
Kramer recently talked exclusively with Kelly about the possibility of a dirty bomb, but now sources said the classroom drills might have to be put into practice. Intelligence sources said the terrorists could be trying to make a dirty bomb this time my mixing radiological isotopes with an explosive device.
That's why the NYPD is deploying all kinds of radiation detectors, panel trucks with sophisticated instruments. On Friday, cops had personal radiation detectors on their belts, and radiation detectors are being used by police within a 50-mile radius of New York City -- in New Jersey, Connecticut, and Pennsylvania and on Long Island.
Kelly told Kramer the NYPD has units trained to deal with terrorists who have bombs.
"We think about how to handle these people. How do we approach them if we believe they have some device, a bomb, something that's going to explode," Kelly said. "We have to think about tactics and strategies."
On Friday night, tourists and residents in Times Square didn't seem too concerned with the threat of an attack.
"I think it's the safest place on the planet right now," Andre Vriese of California told CBS 2's Sean Hennessey.
"Keep the country safe and keep terrorists out," added Ken Jennings of Brooklyn.
"I mean, it's been how long since 9/11? So we kind of get used to having the security around," said Nigel McFarland of Brooklyn.
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