Alert Partly Based on Lies

Feb. 13 -- A key piece of the information leading to recent terror alerts was fabricated, according to two senior law enforcement officials in Washington and New York.

The officials said that a claim made by a captured al Qaeda member that Washington, New York or Florida would be hit by a "dirty bomb" sometime this week had proven to be a product of his imagination.

The informant described a detailed plan that an al Qaeda cell operating in either Virginia or Detroit had developed a way to slip past airport scanners with dirty bombs encased in shoes, suitcases, or laptops, sources told ABCNEWS. The informant reportedly cited specific targets of government buildings and Christian or clerical centers.

"This piece of that puzzle turns out to be fabricated and therefore the reason for a lot of the alarm, particularly in Washington this week, has been dissipated after they found out that this information was not true," said Vince Cannistraro, former CIA counter-terrorism chief and ABCNEWS consultant.

It was only after the threat level was elevated to orange — meaning high — last week, that the informant was subjected to a polygraph test by the FBI, officials told ABCNEWS.

"This person did not pass," said Cannistraro.

According to officials, the FBI and the CIA are pointing fingers at each other. An FBI spokesperson told ABCNEWS today he was "not familiar with the scenario," but did not think it was accurate.

Despite the fabricated report, there are no plans to change the threat level. Officials said other intelligence has been validated and that the high level of precautions is fully warranted.

New Yorkers Taking Police Presence in Stride

In New York, police are out in force in the subways, at train stations and airports and at the bridge and tunnel crossings into the city with radiation detectors and gas masks. In a press conference this afternoon, Mayor Michael Bloomberg said 16,000 law enforcement officials trained to combat terrorism were deployed in the city. Air patrols have also returned to New York.