As the nation prepares to mark the 10th anniversary of the September 11 this weekend, officials in New York City and Washington D.C. have heightened security in response to a threat of an attack from al-Qaida.
U.S. counterterrorism officials were investigating a credible but unconfirmed threat that al-Qaida plans to detonate car bomb in the vicinity of bridges or tunnels in either New York City or Washington, D.C. to coincide with September 11 commemoration ceremonies.
"As we know from the intelligence gathered from the [bin Laden] raid, al-Qaida has shown an interest in important dates and anniversaries, such as 9/11," Matthew Chandler, a spokesman for the Department of Homeland Security, said in a statement.
"In this instance, it's accurate that there is [a] specific, credible but unconfirmed threat information," Chandler said.
The Washington Post and CBS News report that three people associated with the plot may be traveling to the U.S. or may have entered the U.S. recently. The individuals are believed to have traveled from tribal areas of Pakistan along the Afghan border; one person is speculated to be a U.S. citizen.
Increased police presence has been put into effect in both New York City and Washington D.C.
Washington D.C. law enforcement officials are on indefinite 12-hour shifts. Police Chief Cathy Lanier announced that abandoned or suspicious vehicles are subject to being towed and loitering people apprehended.
Police Commissioner Ray Kelly announced that NYPD tours have been extended by four hours through Monday. Increased patrolling will also be established at bridges, tunnels and landmarks, such as Grand Central Station, Penn Station and Times Square.
There will also be an increased presence of bomb-sniffing dogs, more car checkpoints, increased towing, and more subway bag checks.
Mayor Michael Bloomberg rode the subway to work Friday to show that all precautions were being made to keep NYC's public transportation system safe.
"We take every single threat that is credible seriously," he told the Associated Press. "We may feel that it's more likely or less likely but you never want to say 'well we didn't think that was very likely' so we didn't do anything."