The agents, armed with a search warrant, arrived late Wednesday afternoon at the Aurora, Colo., apartment of Najibullah Zazi, ABC News reported. FBI officials would not comment on what the search of the apartment or another search of the Denver home of Zazi's aunt, Rabia Zazi, had turned up, ABC said.
Zazi's trip to New York City last week led to raids of homes in the city's Queens borough. Authorities told members of Congress those raids helped to disrupt a plot to attack the city, ABC said.
The network quoted unidentified law enforcement officials as saying the New York raids turned up 14 new backpacks, fueling concern terrorists may have planned to use the backpacks to carry suicide bombs. Zazi also had allegedly brought to New York instructions on how to build a bomb using household chemicals, ABC said.
Zazi, 25, an Afghan emigre, has not been charged. He told ABC News' Denver affiliate Tuesday that he had no connections to al-Qaida and said the FBI "got it wrong."
"I have nothing to do with al-Qaida -- any link or anything with al-Qaida," Zazi said.
His attorney, Arthur Folsom, said he had planned to take Zazi to the FBI office in Denver "to remove this dark cloud hanging over him."