After warnings of a possible 9/11 anniversary terror plot, FBI Joint Terrorism Task Force officials across the country are now conducting interviews to eliminate hundreds of people who could match travel patterns of terrorists.
Intelligence collected from overseas indicates a possible threat involving car bombs, as well threats to bridges and tunnels, according to a security official. The information indicated that three men would travel from Pakistan to the U.S. to carry out an attack.
A government official stresses security officials do not know if any terror suspect entered the United States at all, and the questioning of travelers across the country is precautionary and is meant to rule people out.
Several intelligence, law enforcement and Homeland Security officials said Saturday that after intensive checking of records and sources, there's still nothing to confirm the warning of a vehicle bomb plot around 9/11, which came from a Pakistani intelligence source.
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Airline passenger arrival records are being checked against the few vague details the source offered, including age range, approximate heights, fragments of names, and travel patterns.
That chore is complicated by the possibility that the men may have been smuggled into and out of Pakistan, leaving no record they were ever there.
Law enforcement officials say hundreds of recent arrivals have already been checked and ruled out. Some of that can be done merely by reference to the records, but in other cases, in-person interviews are being conducted.
And around New York and Washington, officials say the FBI has found no sign of unusual purchases of chemicals needed to make car bombs.
A joint FBI-Department of Homeland Security bulletin from Thursday said al-Qaida may be considering attacks that use improvised explosives packed in vehicles, similar to the "attempted attack on Times square" by Faisal Shahzad in May 2010.
Al-Qaida may be aiming to avenge the death of Osama bin Laden and other key terror figures, the bulletin said.
Also Saturday, officials were investigating information about two construction vans stolen along roads in Queens on Sept. 1 or 2. A government official says the theft may have been from somebody working with the van, theorizing that it may be an inside job.
Along with the vans, $70,000 in construction equipment was reported stolen.
The alleged terror threat by al-Qaida against New York City and Washington D.C has brought additional police officers, vehicle checkpoints, and subway bag checks.
The NYPD has increased already-tight security because of the intelligence, which indicates a possible car bomb plot, officials said.
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