Concerned about the threat of a retaliatory terror attack following the death of Osama bin Laden, federal officials sent out a bulletin warning agencies that the al-Qaida leader's death could "inspire violent extremist followers or lone offenders" to try to strike.
A U.S. Department of Homeland Security spokeswoman said there is no specific threat at this time. But officials remain concerned about a possible so-called "lone wolf" terror plot.
"We have no credible information to suggest that a specifically targeted plot is underway," the DHS spokeswoman said.
Police Commissioner Ray Kelly has said that while the latest warnings are not specific to New York, the city has been the target of a dozen failed plots since 9/11 and remains at the top of terrorists' lists.
The weekend bin Laden was killed was also the one-year anniversary of the plot to bomb Times Square. While Faisal Shahzad did receive some terror training overseas, he picked the target and drove the faulty car bomb from Connecticut into Midtown.
The lone wolf advisory reminds law enforcement officials of past homegrown attacks and urges them to consider the possibility that "lone offenders -- who are unburdened by organizational constraints that can slow operational decisions by established terrorist groups -- could attempt a near-term attack using simple improvised explosive devices (IEDs) or small arms tactics against easily accessible, low security targets."
Law enforcement officials have been on high alert in recent days.
In New London, Conn. on Tuesday, the FBI and a state police bomb squad responded to a report of a suspicious package left near a bus depot and rail line. The box was detonated and determined not to be a threat.
This response comes after New York police responded overnight Sunday to a minivan with two dozen "pipe-like devices and wires" inside.
The vehicle was parked outside Lincoln Hospital but was left with its engine running and there was a cell phone plugged in.
An "all clear" was later given by the bomb squad. It turns out the driver apparently parked the car there and rushed into the hospital for help for an asthma attack.