Adis Medunjanin, a Bosnian immigrant and Zarein Ahmedzay, a 24 year old New York City cab driver, have not been charged with any crime.
But both men accompanied Zazi to the tribal region of Pakistan recently where Zazi received instructions on bombing making and weapons use at the al Qaeda terrorist camps, according to investigative sources.
Investigators have not determined whether Zazi's two associates, Medunjanin and Ahmedzay also received training at the camps but they suspect that they at least visited them during their trip and received some level of training, sources said.
Medunjanin's attorney Robert Gottlieb said Medunjanin knew Zazi from the neighborhood in Flushing, Queens where both men were raised. Gottlieb declined to comment on whether Medunjanin had recently seen Zazi or whether he had traveled overseas.
Medunjanin is an American citizen who hold a Masters Degree in Economics and is employed at a building management company in New York, he said.
"This has been a nightmare for him and his family," said Gottlieb. He said that Medunjanin was questioned voluntarily by the FBI for more than 14 hours and that the FBI under a search warrant seized numerous items from his apartment including a computer, cell phone and various documents.
Sources told CBS News that intercepted phone calls of Zazi's to associates in New York while he was driving from Colorado to New York prior to the weekend of the 8th anniversary of 9/11, he had discussions with how to build a bomb and what ingredients he was going to use.
"The assessment is that he (Zazi) is clearly capable of making a bomb," one source said. "He knew what he was doing."
Law enforcement is monitoring between two to six people in the plot investigation, sources said. And they continue to search for a stockpile of bomb making ingredients.
But there is nothing to indicate that a plot is advancing and no arrests appear to be immediate - a situation that could change in a moments notice.
Investigators are closely looking for a crack in the door of these associates to try to determine if any of them can be tied to a crime, sources say.
"Zazi's associates now seem burrowed in a hole. All being good citizens," a source said.