NYC on Terror Alert as 9/11 Anniversary Approaches

As America prepares to mark the 10th anniversary of 9/11, New York City is on a heightened terror alert, thanks to a credible but unconfirmed threat about a car bomb in New York or Washington, D.C. INSIDE EDITION reports.

New York City is on lockdown as authorities search for three terrorists on a mission to mark the anniversary of 9/11 with another attack.

Any truck that could be used to carry a bomb was stopped and searched at checkpoints across the city and on the George Washington Bridge.

News of the terror threat broke just as President Obama finished his historic address to Congress on jobs.

Events drawing big crowds, including the U.S. Open tennis tournament, New York Fashion Week shows, and the 9/11 commemoration at Ground Zero, are considered potential targets.

Despite the threat, First Lady Michelle Obama attended the U.S. Open with daughters Sasha and Malia.

Mayor Mike Bloomberg rode the subway Friday morning to reassure anxious New Yorkers the city is safe.

Street vendor Duane Jackson saved Times Square from a terrorist bomb in May 2010, alerting cops after spotting a suspicious vehicle. He was in his usual spot Friday and still on the lookout for terrorists.

"Don't take anything for granted, you know, a lot of times we'll walk by something and just slough it off type of thing, but certainly in this day and age, and certainly the May 1st incident, illustrates that we've all got a hand in our own safety," Jackson said.

What would have happened if that car bomb had exploded? Experts at the New Mexico Institute of Mining and Technology put together a similar device for INSIDE EDITION.

We placed some mannequins at varying distances around an SUV for a test detonation to show what might happen if a car bomb went off in a very busy Times Square.

The blast zone would have extended 50 feet. A fireball would reach out 400 feet. Car parts would have caused injuries and damage 500 feet away and up to 20 stories high!

As the dust cleared, the area of debris was bigger than a football field. All that was left of a mannequin that had been directly behind the SUV during the explosion was the shoes.

INSIDE EDITION went to Times Square with counterterrorism expert Patrick Devlin, who spotted a suspicious vehicle.

"That to me is something that, under a heightened state of alert, would need to be investigated, would need to be looked at," he said of a parked black van.

So how can you help foil a terrorist plot?

"Look for vehicles parked in loading docks, the loading dock areas, bus stops, taxi stands, passenger pick-up areas; a bad guy is not going to take the time to find a legal parking spot, they're going to put that vehicle as close to a target building as possible, in any space available," Devlin said.

As we remember the events of 9/11, the newest threat is a grim reminder that America remains the target of terrorists.