Sept. 25: Najibullah Zazi, center, is escorted off an NYPD helicopter by U.S Marshals after being extradited from Denver, Colo.
Najibullah Zazi arrives at the offices of the FBI in Denver for questioning on Thursday, Sept. 17, 2009.
The three suspects in a possible Al Qaeda-linked train bomb plot.
Sept. 19: Terrorism suspect Najibullah Zazi is arrested by FBI agents in Aurora, Colo.
Sept. 18: Mohammed Zazi
Federal agents are seen outside Najibullah Zazi's door as they conduct a search of his apartment in Aurora, Colo, on Sept. 16.
Sept. 22: Washington police cars are stationed outside the Verizon Center stadium, where the Wizards play basketball and the Capitals play hockey, after a federal alert in a terror probe went out to police to keep an eye on sports arenas and other spots.
An Afghan immigrant accused of plotting a terrorist attack in New York after receiving training in Pakistan was in contact with a senior Al Qaeda operative, intelligence officials familiar with the investigation told The Associated Press.
The CIA learned about Najibullah Zazi through one of its sources and alerted domestic agencies, including the FBI, intelligence officials said. The officials, who declined to offer more details on the operative, spoke on condition of anonymity because the investigation is ongoing.
The fact that intelligence officials learned of Zazi through a CIA source sheds more light on the government's claim that the charges against Zazi are part of a broader, international case and begins to explain why the investigation triggered such a large offensive from the nation's intelligence community.
It also shows the case stems from the CIA's counterterrorism efforts to track Al Qaeda and not an investigation initiated in this country by someone's suspicious actions, like most other domestic terrorism cases handled by the FBI.
President Barack Obama received briefings on the investigation as intelligence officials were crafting their case against Zazi, a White House official familiar with those updates said. The official, who was not authorized to speak about the case publicly, spoke on condition of anonymity.
The CIA declined to comment for this story, spokesman George Little said.
Speaking Monday in Colorado at a conference of police chiefs, Attorney General Eric Holder said the plot had the potential to kill scores of people.
Zazi, 24, is the only suspect publicly identified in the terror plot. More arrests are expected. Prosecutors have said three others in New York City worked with Zazi, although they do not currently pose a threat.
Calls to Zazi's lawyer were not returned Monday.
Zazi was arrested last month initially on charges that he lied to federal investigators. He remains held without bond and has pleaded not guilty to conspiring to use weapons of mass destruction. The charges related to his statements to investigators later were dropped.
Zazi's father, Mohammed Wali Zazi, and a Queens, New York, imam, Ahmad Wais Afzali, face charges of lying to investigators last month when first questioned about Zazi.
Prosecutors said Zazi received explosives training at an Al Qaeda training camp. They have accused him of planning an attack in New York, perhaps on the city's subway system around the anniversary of the 9/11 World Trade Center attack, using powerful homemade bombs of hydrogen and flour.
Would-be shoe bomber Richard Reid attempted to use the same type of explosive in 2001 and the material was used by the terrorists in the London bombings in 2005 that killed 52 people.
Zazi received the training to make the bombs from common supplies purchased at beauty supply stores after making contact with Al Qaeda, intelligence officials said, although they declined to say when that occurred. Zazi's contact with the senior Al Qaeda operative occurred through an intermediary, one official said.
Zazi, who moved to the U.S. with his family as a teenager, has denied any involvement in a terror plot. He has said his travels to Pakistan, which began in 2006, were to visit family, including his wife, whom he married on that first trip.
The case against Zazi involves classified information as well as evidence the FBI collected in searches of Zazi's computer that discussed bomb making.
Prosecutors submitted court documents saying they intend to use electronic information the FBI obtained through the use of the Foreign Intelligence Surveillance Act.