Napolitano urges vigilance for 9/11 anniversary

Homeland Security Secretary Janet Napolitano is asking the public to remain vigilant and report suspicious activity to authorities as the 10th anniversary of the Sept. 11 terrorist attacks approaches.

Napolitano issued her plea Friday as federal authorities continued investigating a "recent specific, credible but unconfirmed threat" that suggested al-Qaida terrorists may be planning an attack in Washington or New York to coincide with the weekend anniversary.

She said homeland security is a shared responsibility and urged people "if you see something, say something."