Najibullah Zazi _ a 24-year-old airport shuttle driver who authorities said received explosives and weapons training from al-Qaida during a trip to Pakistan last year _ was charged in New York with conspiracy to use weapons of mass destruction.

His arrest in Denver a week ago on charges that he lied to terrorism investigators sparked home and business searches in New York and Denver, as well as a flurry of national warnings of possible bomb attacks on transit, sports and entertainment complexes.

Authorities hadn't determined a time and place of a possible attack, and Attorney General Eric Holder said in Washington, "We believe any imminent threat arising from this case has been disrupted."

Counterterrorism agents have said they feared Zazi and others might have been planning to detonate homemade bombs on New York City commuter trains.

The two-page indictment of Zazi, who appeared in a Denver court on Thursday, offers few details, but a separate document _ a government motion seeking to deny bail _ lays out evidence gathered by investigators.

The airport shuttle driver began plotting to "use one or more weapons of mass destruction" between Aug. 1, 2008, and September 2009 against the United States, the papers say.

The document says that on Sept. 6 and 7, Zazi tried to communicate with another individual "seeking to correct mixtures of ingredients to make explosives."

"Each communication," the papers say, was "more urgent than the last."

On those days, Zazi rented a suite at a hotel in his hometown of Aurora, Colorado, authorities charge. The room had a kitchen, and subsequent FBI testing for explosives and residue in the suite found the presence of residue in the vent above the stove.

In July and August, Zazi bought unusually large amounts of hydrogen peroxide and acetone _ a solvent commonly found in nail polish remover _ from beauty supply stores in the Denver metropolitan area, the document says. He searched the Internet for home improvement stores in Queens before driving a rental car for a two-day trip to the city, the document says.

A senior official familiar with the investigation said Zazi had associates who visited Colorado from New York to help him buy the chemicals. The official, who spoke on condition of anonymity because the case is ongoing, said they used stolen credit cards to make the purchases and then returned to New York.

The official did not say whether the associates included those already charged or whether they were new to the investigation.

Zazi has publicly denied any terrorist plotting. But a series of searches in Denver and New York City over the past two weeks _ including high-profile raids on Queens apartments that netted backpacks, cell phones and a scale _ haven't found any evidence of explosives. Authorities say they found bomb-making instructions on a hard drive on Zazi's laptop computer.

Beauty supply store employees in New York and the Denver suburbs said authorities had been there recently asking whether large quantities of hydrogen peroxide or acetone supplies had been purchased.

At Hidden Beauty in Queens' Flushing neighborhood, a quick walk from the apartment where Zazi stayed this month, a plainclothes officer stopped by and asked whether anyone had been there to buy a large amount of acetone, store employee Sam Chin said Thursday. The manager told him that no one had, Chin said.

John Choy, a salesman for 707 Beauty Supply and Fashion Plus in the Denver suburb of Aurora, said FBI agents went to his store about two weeks ago and asked him whether he sold hydrogen peroxide to anyone recently. Choy said that the store sells only a few small bottles a year and that no one who bought it fit the description of Zazi.

Zazi's father, Mohammed Wali Zazi, and a New York City imam, Ahmad Wais Afzali, also appeared in court Thursday on charges of lying to investigators of the terror plot.

Mohammed Zazi was ordered in Denver to be freed under court supervision until an Oct. 9 hearing, although authorities planned to transfer him soon to New York. Afzali was released in New York on $1.5 million bond.

Afzali's attorney, Ron Kuby, denied that his client _ who authorities said helped tip Zazi off with a phone call that investigators had been asking about him _ knew anything about a plot.

"Obviously, the government would not be consenting to bail if it thought he was involved in a terrorism conspiracy," he said.

A second, unrelated indictment unsealed Thursday in the same court charged a Brooklyn man with supporting terrorism in what authorities say is an investigation. An indictment alleges Betim Kaziu traveled to Pakistan this year to try to receive training from a militant group linked to al-Qaida, and tried to go to Afghanistan and Iraq to fight against U.S. forces there.

Kaziu was to be arraigned later Thursday. Prosecutors did not have the name of his attorney.

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Barrett reported from Washington. Associated Press writers Steven K. Paulson and P. Solomon Banda in Denver and Samantha Gross in New York contributed to this report.