UPDATE 4-U.S. charges Afghan-born man with bombing plot

* Indictment alleges Zazi bought chemicals to make bombs

* U.S. attorney general says imminent threat disrupted

* Two others arrested in the case are granted release

(Adds bail rulings and release of two other suspects)

By Edith Honan

NEW YORK, Sept 24 (Reuters) - A Colorado airport shuttle bus driver was charged under federal anti-terrorism laws with plotting to set off explosives in the United States, accused of acquiring the same bomb-making chemicals used in the 2005 London transit attacks.

Najibullah Zazi, 24, an Afghan immigrant already under arrest in Colorado on another charge, was indicted by a grand jury on suspicion of conspiracy to use weapons of mass destruction, authorities announced on Thursday.

No potential targets were revealed, but U.S. Attorney General Eric Holder said the investigation had thwarted any imminent threat. Court documents also referred to unidentified co-conspirators who helped Zazi buy chemicals and with whom he was said to be urgently consulting on how to make explosives.

Prosecutors allege Zazi received al Qaeda training in Pakistan on how to make bombs, possessed detailed notes on his laptop computer on how to assemble them, and accumulated large quantities of bomb-making chemicals. He may have experimented with these chemicals in a bomb-making trial in a Denver hotel room as recently as Sept. 7, they said.

Law-enforcement experts have called the case, if proven, one of the most significant security threats on U.S. soil since the attacks of Sept. 11, 2001.

Two other men arrested at the same time -- Zazi's father and an imam who police say tipped off Zazi that he was under investigation -- were released from jail on Thursday, one on bail and the other under house arrest. They are charged with the lesser offense of lying to the FBI.

The conspiracy charge against Zazi, who immigrated from Afghanistan and is now a permanent U.S. resident, carries a maximum penalty of life in prison if he is convicted.

Authorities have said they had no information on the timing, location or target of any attacks.

"We are investigating a wide range of leads related to this alleged conspiracy," Holder said in a statement. "We believe any imminent threat arising from this case has been disrupted."

EXPLOSIVE CHEMICALS

The U.S. government said that over the last three months Zazi and unnamed associates bought "unusually large quantities" of hydrogen peroxide and acetone products from beauty supply stores in the Denver area that could be used to make triacetone triperoxide, the explosive used in the 2005 London transit bombings that killed 56 and wounded 700. [ID:nN24364730]

Zazi has maintained his innocence since it became apparent he was at the center of an investigation 10 days ago when the FBI and New York City police raided apartments he had visited the borough of Queens.

After returning to his home in Colorado, Zazi voluntarily submitted to questioning by the FBI and was then arrested and charged with lying to the authorities.

His father was also arrested in Colorado, while a New York City imam and police informant was picked up in New York, accused of tipping off Zazi that he was the subject of an investigation and then lying about it to the FBI.

The imam, Ahmad Wais Afzali, was granted bail by a judge and was released on a $1.5 million bond, secured by a $500,000 property where he lives in Queens. He will be on electronic monitoring.

"Obviously the government would not be consenting to his release if they genuinely believed that he was involved in a terrorist conspiracy," Afzali's lawyer, Ron Kuby, told reporters outside a Brooklyn courthouse.

In Denver, a judge released Zazi's father, Mohammed Wali Zazi, 53, into house arrest, but he could not immediately leave custody because he had nowhere to go. He has been evicted from his home in the Denver suburb of Aurora.

Federal authorities said they would ask the court to deny bail to Zazi, calling him a danger to society and a risk for flight to Afghanistan, where his wife and children may reside.

All three Afghan-born men have been accused of lying to the FBI, which carries an 8-year maximum sentence. Prosecutors were seeking to drop the lying charge against Zazi so they could more easily move him to Brooklyn federal court to face trial. (Additional reporting by Jeremy Pelofsky and James Vicini in Washington and Robert Boczkiewicz and Keith Coffman in Denver; Writing by Daniel Trotta; Editing by Steve Gorman and Chris Wilson)