[Updated at 10:05 p.m. ET] New York Police Commissioner Ray Kelly told reporters Thursday night that authorities are "taking additional precautions" given "new threat information" tied to the 10th anniversary of the September 11, 2001, terrorist attacks.

These measures include "vehicle checkpoints around the city," more bomb-sniffing dogs around the city, increased towing of illegally parked cars and greater police staffing, according to Kelly.

[Updated at 9:56 p.m. ET] New York City Mayor Michael Bloomberg told reporters Thursday night that while additional police will be deployed around the city amid reports of an "unconfirmed" terror threat to the city on September 11, "there's no reason for any of the rest of us to change ... our daily routines."

In an earlier statement, New York Gov. Andrew Cuomo urged residents to be "cautious and aware" while adding, "There is no reason to panic." And D.C. Metro Police Chief Cathy Lanier said that authorities in the nation's capital are preparing for 9/11 anniversary events and noted "maintaining a certain sense of unpredictability is essential to the success of any security plan."

[Updated at 9:53 p.m. ET] U.S. officials said Thursday evening they have "specific, credible but unconfirmed" information about a potential threat against the United States coinciding with the 10th anniversary of the September 11 terrorist attacks.

"We have received credible information very recently about a possible plot directed at the homeland that seems to be focused on New York and Washington, D.C.," a senior administration official told CNN Pentagon Correspondent Barbara Starr.

The official said the plot was believed to involve three individuals, including a U.S. citizen. U.S. officials believed the threat was a vehicle laden with explosives, but "the intelligence picture is not completely formed," the official said. "Not enough is known about the potential operatives and their plotting."

Another source gave CNN conflicting information about possible details of the threat.

A senior law enforcement official involved in briefings about the matter told CNN Justice Department Producer Terry Frieden that his best information is that the three individuals had not yet entered the United States.

The information came in around noon Wednesday, one official said.

A senior federal law enforcement official intimately involved in counterterrorism efforts told CNN Chief National Correspondent John King authorities "aren't sure if this is or real or just chatter." The official confirmed the threat was vehicle-related.

Officials said they were taking the threat seriously, while evidently trying to temper the news by saying such threats are commonplace during key events.