A U.S. official tells FOX News that documents seized in Iraq last year by American forces suggest Al Qaeda in Iraq was plotting an attack inside the United States by smuggling terrorists into the country on student visas.

The papers were obtained in Iraq about the time that Al Qaeda in Iraq leader Abu Musab al-Zarqawi was killed last June, the official, who asked not to be identified, told FOX News.

Defense Intelligence Agency chief Lt. Gen. Michael Maples referred to the scheme Jan. 11 when he told the Senate Intelligence Committee that "documents captured in a raid on an Al Qaeda in Iraq (AQI) safehouse revealed AQI was planning terrorist operations in the U.S.," according to the source.

But there's no indication the documents were new when they were found — and at least one of those suspected of planning the attack has since been "put out of commission," the official said.

In fact, the source said, the U.S. government doesn't believe the plot ever got off the ground — but instead was disrupted.

Two years ago, U.S. counterterrorism officials obtained a letter from Usama bin Laden's deputy Ayman al-Zawahiri to Zarqawi calling on him to strike Americans rather than Iraqi Shiites and to expand his attacks beyond Iraq. In light of that correspondence, American officials said the latest student visa plot to wage an attack within the United States was no surprise.

Zarqawi was killed last June in a U.S. airstrike near Baqubah, Iraq. Al Qaeda in Iraq is thought to be an Iraq-based faction or offshoot of the terrorist network Al Qaeda.