Officials tell ABC News they know of three distinct teams of four men each, but there may be others linked to the plot that remain unidentified.
Law enforcement agents say they're watching a number of people on round-the-clock surveillance who they suspect might have been part of the alleged terror cell.
Suspects Najibullah Zazi, a 24-year-old airport shuttle driver, and his father Mohammed made their first court appearance in a Denver federal courtroom today, handcuffed and dressed in the same clothes they were arrested in Saturday night.
They are charged with lying to federal agents during an investigation into the alleged terror plot that has been described as "the real deal" by authorities.
Zazi, who authorities say appears to be the ringleader of the alleged plot, has been tracked by the FBI and the CIA for more than a year, during which time he has traveled twice to Pakistan for explosives training from al Qaeda.
Officials say they do not have specifics on the potential targets of the alleged plot, which may have been the most serious plan against the U.S. since 9/11.
Court records show Zazi ran up more than $50,000 in debt on 20 credit cards, leading to concerns he was preparing for a suicide mission.
He declared Chapter 7 bankruptcy in Mar. 2009, and while he told investigators he had been traveling to Pakistan see his wife, he checked the "not married" box on his application form.
In a criminal complaint, the FBI alleges they found nine handwritten pages on the manufacture and handling of explosives, detonators and the fusing system in Zazi's possession.
"When [Zazi] was questioned about whether or not he knew anything about these written notes, and they were shown to him, he denied that knowledge," said NYPD Commissioner Ray Kelly.
Kelly said Mohammed Zazi was arrested "because he lied about the phone call that he made to his son when he was in New York."
Read more and source: ABC News