U.S. Homeland Security Secretary Janet Napolitano says there is no "credible intelligence" that al-Qaida or its affiliates are plotting attacks in the United States to coincide with the tenth anniversary of the September 11, 2001 terrorist attacks.
But Napolitano says officials remain at a heightened state of vigilance. Her statement Friday said security measures are in place to detect and prevent plots against the United States should they emerge.
Meanwhile, the U.S. government is telling Americans abroad to take precautions.
The State Department issued a worldwide travel alert Friday, cautioning U.S. citizens traveling and living outside the country about what it called the "continued threat" posed by al-Qaida.
The department said it has not identified any specific threats, but said U.S. citizens should be aware that al-Qaida affiliates have demonstrated the intent and capability to carry out attacks against the U.S. and its interests around the world. The statement said terrorist organizations have planned attacks before to coincide with significant dates.
Throughout the United States, law enforcement agencies have been enhancing security in places that might be terrorist targets. One of those places is New York City, where most of the deaths occurred in the 2001 attacks.
Nearly 3,000 people were killed when al-Qaida terrorists hijacked four U.S. commercial airplanes and flew them into New York's World Trade Center towers and the Pentagon outside Washington. The fourth plane crashed in Pennsylvania as passengers and crew fought their hijackers.
Police are especially concerned because evidence reportedly recovered at late al-Qaida leader Osama bin Laden's compound indicated he was encouraging al-Qaida operatives to attack the United States on, or around, September 11th.
Bin Laden, who was killed in May in a U.S. raid, reportedly wanted to fly a small plane into a sporting event to cause mass casualties.
Al-Qaida's new leader, Ayman al-Zawahiri, has also appeared in numerous videos calling for attacks against U.S. targets and urging Muslims to support his cause.
Analysts say another threat is from so-called homegrown terrorists in the U.S. who have been radicalized on the Internet.
In the last decade there have been at least 38 plots by homegrown terrorists. Among them was Pakistani-born U.S. citizen Faisal Shahzad, who in 2010 tried to set off a car bomb in New York's Times Square. Afghan immigrant Najibullah Zazi pleaded guilty last year to a 2009 plot to bomb New York City subways.
Some information for this report provided by Reuters.