Officials: No known Independence Day threat

WASHINGTON (CNN) -- There is no credible information that terrorists are plotting an attack to coincide with the Fourth of July holiday, federal law enforcement officials said.

Nevertheless, there will be a strong security presence at big crowd events, particularly in New York City and Washington, cities hit hard during the September 11, 2001, terror attacks.

After al Qaeda leader Usama bin Laden was killed by U.S. Navy Seals during a May 2011 raid, material found at his compound in Abbottabad, Pakistan, indicated the terror group was interested in striking on significant dates such as Independence Day and Christmas.

Although there is no intelligence indicating an al Qaeda plot tied to July 4, law enforcement remains watchful. And officials never rule out the possibility that a single person, a so-called lone wolf, might choose to commit an act of violence at a holiday gathering.