A previous version of this report appeared on World News and abcnews.com on Monday, January 22, and inaccurately stated that the 9/11 hijackers used student visas to gain entry to the United States. Only one of the 9/11 hijackers entered the U.S. on a student visa; the remaining hijackers were admitted on tourist and business visas. This report has been corrected to address the error.
Insurgents reportedly tied to al Qaeda in Iraq considered using student visas to slip terrorists into the United States to orchestrate a new attack on American soil.
Lt. Gen. Michael D. Maples, head of the Defense Intelligence Agency, recently testified that documents captured by coalition forces during a raid of a safe house believed to house Iraqi members of al Qaeda six months ago "revealed [AQI] was planning terrorist operations in the U.S."
At the time, Maples offered little additional insight into the possible terror plot. ABC News, however, has learned new details of what remains a classified incident that has been dealt with at the highest levels of government.
Sources tell ABC News that the plot may have involved moving between 10 and 20 suspects believed to be affiliated with al Qaeda in Iraq into the United States with student visas.
U.S. officials now require universities to closely track foreign nationals who use student visas to study in the United States. University officials must report international students who fail to arrive on campus or miss class regularly.
In August, the FBI and U.S. Immigration and Customs Enforcement alerted intelligence agencies and state and local law enforcement about 11 Egyptian students who had failed to report to their classes at Montana State University. The students were ultimately apprehended.
Still, despite the heightened precautions, some security analysts fear that skilled terrorists -- handpicked because of their clean records and because they are carefully trained -- could still slip through an academic setting.
The plot was discovered six months ago, roughly the same time that Abu Musab al-Zarqawi, the leader of al Qaeda in Iraq, was killed by coalition forces. Sources tell ABC News that the suspects involved in the effort to launch the U.S. attack were closely associated with Zarqawi.
The plan also came only months after Ayman al-Zawahiri, al Qaeda's No. 2, had requested that Zarqawi attempt an attack inside the United States.
"This appears to be the first hard evidence al Qaeda in Iraq was trying to attack us here at home," said ABC News consultant Richard Clarke, former chief counterterrorism adviser on the U.S. National Security Council.
The plan was uncovered in its early stages, and sources say there is no indication that the suspects made it into the United States. Officials also emphasize that there is no evidence of an imminent attack.
The hunt for suspects continues, however, and some fear that al Qaeda recruits in Iraq could be easily redirected.
"Anyone willing to go to Iraq to fight American troops is probably willing to try to come to the United States," Clarke said.