By Newsmax Wires

WASHINGTON — A manhunt is under way in the United States for two or three suspects linked to a credible but unconfirmed al-Qaida car bomb threat in New York or Washington ahead of the 10th anniversary of the Sept. 11, 2001, attacks.

Both Reuters and The Associated Press quoted anonymous sources as claiming that two or three people, possibly with al-Qaida ties, are being sought.

Three people being investigated recently entered the United States, The Associated Press Reported. The threat came in a single piece of information and was so specific — and came at such a time of already heightened alert — that it could not be ignored, according to AP, quoting officials on condition of anonymity because of sensitive security matters.

But James McJunkin, the assistant director in charge of the FBI’s Washington field office, said his agents aren’t seeking any particular individuals.

One person familiar with the matter said those being sought are suspected of having ties to al-Qaida, Reuters reported. But the officials used strong caveats when discussing the threat information privately, with a national security official cautioning that experts believe the investigation will not pan out.

The threat involves a detailed al-Qaida car bomb plot aimed at bridges or tunnels in New York or Washington, the wire services quoted anonymous authorities as saying.

The threat prompted President Barack Obama to order counterterrorism forces to increase security measures. “The president directed the counterterrorism community to redouble its efforts in response to this credible but unconfirmed information,” said a White House official.

The threat came in late Wednesday night and is the first tip the U.S. intelligence community has received about an “active plot” targeting the anniversary, officials said.

In New York City, Mayor Michael Bloomberg said at a news conference about 10 p.m. that security was increased there because of the threat but said city residents should go about their business as usual.

“The NYPD is deploying additional resources around the city and taking additional steps to keep our city safe, some of which you may notice and some of which you will not notice,” Bloomberg said. “But there’s no reason for any of the rest of us to change anything in our daily routine.”

Bloomberg said the threat has not been corroborated but that it is credible, and he urged residents should be vigilant.

And in the nation’s capital, law enforcement officials say they are working to corroborate a terrorism threat against the city. Police Chief Cathy Lanier says that all police officers will be working 12 hour days indefinitely. She says unattended cars parked in odd locations risk being towed in the next few days.

“The context is still forming,” a U.S. official cautioned, adding the threat appears to be connected to Washington and New York City but that other cities could not be ruled out.

The Department of Homeland Security issued a statement saying, “As we know from the intelligence gathered from the Osama bin Laden raid, al-Qaida has shown an interest in important dates and anniversaries, such as 9/11.

“It’s accurate that there is specific, credible but unconfirmed threat information,” Homeland Security Department spokesman Matt Chandler said. “As we always do before important dates like the anniversary of 9/11, we will undoubtedly get more reporting in the coming days.”

Law enforcement officials are checking out all of the details included in the threat, said Rep. Peter King, R-N.Y. “No need to panic,” King said. “They have not been able to confirm it yet.”

An administration official told NBC News that the threat “so far” was a 5 to 6 on a scale of 10.