America remains at heightened vigilance against possible threats as the 10-year anniversary of the 9/11 attacks nears, Secretary of Homeland Security Janet Napolitano said Friday.

"As we approach the tenth anniversary of the September 11, 2001, terrorist attacks, the safety and security of the American public remains our highest priority," Napolitano said in a statement.

"While there is no specific or credible intelligence that al-Qaida or its affiliates are plotting attacks in the United States to coincide with the ten year anniversary of 9/11, we remain at a heightened state of vigilance and security measures are in place to detect and prevent plots against the United States should they emerge," she said.

The secretary's remarks came as President Barack Obama is scheduled to attend a host of events this month marking the anniversary, including memorials in New York, northern Virginia and Pennsylvania.

In all, more than 3,000 people were killed in in the U.S. terrorist attacks on the morning of Sept. 11, 2001. Terrorists hijacked three passenger jets and crashed them into World Trade Center in New York City, the Pentagon in Arlington, Virginia, and Shanksville, Pennsylvania.