DENVER — Counterterrorism officials are warning mass transit systems around the nation to step up patrols because of fears an Afghanistan-born immigrant under arrest in Colorado may have been plotting to detonate backpack bombs aboard New York City trains.
Investigators say Najibullah Zazi, a 24-year-old shuttle van driver at the Denver airport, played a direct role in a terror plot that unraveled during a trip to New York City around the anniversary of the Sept. 11 attacks. He made his first court appearance Monday and remained behind bars.
Zazi and two other defendants have not been charged with any terrorism counts, only the relatively minor offense of lying to the government. But the case could grow to include more serious charges as the investigation proceeds.
Zazi has publicly denied being involved in a terror plot, and defense lawyer Arthur Folsom dismissed as “rumor” any notion that his client played a crucial role.
Publicly, law enforcement officials have repeatedly said they are unaware of a specific time or target for any attacks. Privately, officials speaking on condition of anonymity because they were not authorized to discuss the case said investigators have worried most about the possible use of backpack bombs on New York City trains, similar to attacks carried out in London and Madrid.
Backpacks and cellphones were seized last week from apartments in Queens where Zazi visited.
In a bulletin issued Friday, the FBI and Homeland Security Department warned that improvised explosive devices are the most common tactic to blow up railroads and other mass transit systems overseas. And they noted incidents in which bombs were made with peroxide.
In the bulletin, obtained officials recommended that transit systems conduct random sweeps at terminals and stations and that law enforcement make random patrols and board some trains and buses.
The effects of the warning were not immediately clear Monday. New York’s transit agency said it was in touch with an FBI-NYPD task force but wouldn’t comment further.
The task force feared Zazi may have been involved in a potential plot involving hydrogen peroxide-based explosives, according to two law enforcement officials, who spoke on condition of anonymity because they were not authorized to discuss the investigation.
Investigators said they found notes on bomb-making instructions that appear to match Zazi’s handwriting, and discovered his fingerprints on materials — batteries and a scale — that could be used to make explosives. He also made a trip to Pakistan last year in which he received al-Qaida explosives and weapons training, the government said.
Zazi, a legal resident of the U.S. who immigrated in 1999, told the FBI that he must have unintentionally downloaded the notes on bomb-making as part of a religious book and that he deleted the book “after realizing that its contents discussed jihad.”