U.S. Says There is Credible Evidence of 9/11 Al Qaeda Attack

Updated at 10 p.m. edt

There are credible, but unconfirmed threats of a potential Al Qaeda truck-bombing plot aimed at targets in New York City and Washington around the 10th anniversary of the Sept. 11 terrorist attacks, officials confirmed tonight.

"The President was briefed on this specific threat information this morning and has been updated on it throughout the day," a White House official said.

"The United States government has already significantly enhanced its security posture in advance of the 9/11 anniversary to protect the country against possible terrorist threats," the official said.

"Nevertheless, the President directed the counterterrorism community to redouble its efforts in response to this credible but unconfirmed information," the source added.

At least three people from Afghanistan, one possibly an American citizen, flew to the U.S. in August with the potential intent to launch a truck-bomb attack in New York, Washington or both, another government official said, confirming an ABC News report.

Authorities are looking for two rental trucks missing from locations in Kansas City, ABC reported.

New York Mayor Mike Bloomberg later claimed the reports of trucks being involved was debunked and he urged people to go about their normal business.

"What we have to do is not let the terrorists win by intimidation," Bloomberg said.