Prosecutors have said the three others who shopped with him in Aurora, Colo., for the beauty products also accompanied him on an August 2008 flight to Pakistan for terrorism training. By that time, he had already come to authorities' attention.

A criminal complaint has suggested that police acting without the FBI's knowledge might have compromised the investigation and helped blow the surveillance of Zazi by questioning a Muslim religious leader about him.

The imam and Zazi's father face charges of lying to terrorism investigators; they deny the allegations.

As authorities have continued to search for additional suspects, they've issued a flurry of terrorism warnings for sports complexes, hotels and transit systems based on their investigation.

Associated Press