NEW YORK -- An Afghan immigrant pleaded not guilty Tuesday to using beauty products to build bombs for an attack on New York City -- an alleged plot authorities say was helped by at least three accomplices whose whereabouts and level of involvement haven't been revealed.

"The conspiracy here is international in scope," Assistant U.S. Attorney Jeffrey Knox told a federal judge in Brooklyn.

Najibullah Zazi, wearing a blue jail smock, never spoke and showed no emotion as his lawyer entered the plea in a packed courtroom. He was ordered held without bail.

"You get the impression he's a nice guy, don't you?" defense attorney Michael Dowling told the reporters afterward.

The 24-year-old Denver airport shuttle driver has been the only alleged terrorist identified so far. But authorities have said three people traveled from New York City to suburban Denver this summer and used stolen credit cards to help Zazi stockpile products containing hydrogen peroxide and acetone -- common ingredients for homemade bombs.

Dowling admitted that his client visited Pakistan last year, and made purchases earlier this year at a beauty supply shop in Aurora, Colo. But he added, "Those acts are not illegal" and cautioned against a "rush to judgment."

Asked about possible accomplices, the lawyer said, "I don't know the names of anybody else that allegedly conspired with Mr. Zazi. ... Those names have not been produced."

Police Commissioner Raymond Kelly refused Tuesday to discuss the potential of other plotters at large, but insisted there was no threat to the city.

The plot "has been broken up," Kelly said. "I see no danger emanating ... from the people involved in this investigation."

Prosecutors allege that Zazi has admitted that while living in Queens, he went to Pakistan and received explosives training from al-Qaida. Security videos and store receipts show that when he returned and moved to Colorado, he and three others bought several bottles of beauty products over the course of several weeks, court papers said.

On Sept. 6, Zazi took some of his products into a Colorado hotel room outfitted with a stove on which he later left acetone residue, authorities said. He repeatedly sought another person's help cooking up the bomb, "each communication more urgent in tone than the last," the papers said.

The FBI was listening to Zazi and becoming increasingly concerned as the anniversary of the Sept. 11, 2001, attacks and a New York visit by President Barack Obama approached, officials said. After he rented a car on Sept. 9 and drove to New York, investigators say they secretly searched the vehicle and found a laptop computer with bomb-making instructions.

On Sept. 10, Zazi told the Queens imam in an intercepted phone call that he feared he was being watched, court papers said. The imam later tipped Zazi off, saying police had come around and asked questions, the papers said.

Zazi cut short a five-day trip and flew back to Denver on Sept. 12. He was arrested a week later and initially charged along with his father and the imam with lying to investigators.

Zazi's next court date has been set for Dec. 3.