On Friday, New York police had taken additional measures such as blocking off some of the approaches to Grand Central Station, stopping trucks and vans to search their contents, and increasing patrols. In Washington, police began working 12-hour shifts and said unattended vehicles near bridges and monuments would be towed.
One of the major reasons why law enforcement officials are taking no chances is because of intelligence gleaned from computers and notebooks found in the Pakistan compound where Al Qaeda leader Osama bin Laden was killed by US forces on May 2.
“When you see how fixated Osama bin Laden was on the 10th anniversary, it makes sense to have extra precautions during significant dates and events,” says Mr. Cilluffo.
On Sunday, President Obama plans to visit each of the sites hit on Sept. 11, 2001, the World Trade Center, the Pentagon, and the field in Shanksville, Pa., where hijacked flight 93 crashed. The White House says the potential security threat will not change his schedule.