UPDATE 2-FBI question Colorado man linked to NY raid

* DNA, handwriting samples furnished by questioned man

* Investigators search second Denver-area home (Updates with details from Zazi's lawyer)

By Keith Coffman and Robert Boczkiewicz

DENVER, Sept 16 (Reuters) - Federal agents conducting an anti-terrorism probe on Wednesday questioned a suspected al Qaeda sympathizer whose recent visit to New York City preceded a series of law enforcement raids there earlier in the week.

FBI agents interviewed Najibullah Zazi, 24, for several hours at the agency's downtown Denver bureau while simultaneously searching his apartment in suburban Aurora and a nearby house believed to be the home of a relative.

Zazi's lawyer, Art Folsom, told reporters outside the FBI office that his client was cooperating with investigators and had voluntarily given them samples of his handwriting, fingerprints and DNA.

Zazi, who works as an airport shuttle driver, voluntarily paid a visit to the FBI after Folsom contacted the bureau and said they "wanted to come down and talk," the attorney said. Folsom said Zazi's father accompanied his son to the FBI office and furnished handwriting and DNA samples of his own.

"We have answered all the questions that the FBI had for Mr. Zazi," Folsom said, adding, "My client is not involved in any terror plot."

NO IMMINENT THREAT

Earlier in the day, FBI Director Robert Mueller reassured lawmakers in Washington that there was no imminent security threat related to the investigation but declined to elaborate on the probe.

FBI agents entered Zazi's residence on Wednesday afternoon with a search warrant, FBI special agent Kathy Wright said. She declined to give further details.

The entire three-story apartment building was roped off with yellow crime-scene tape, and authorities put black screens over the building's windows to prevent onlookers from seeing inside. A house a few miles away was likewise cordoned off later in the day for what a local law enforcement source said was a search related to the anti-terror investigation.

Before the Denver-area raids began, three local public schools were locked down as a precaution, with students kept inside until they were picked up by their parents.

The questioning of Zazi, who authorities suspect of sympathizing with al Qaeda, came days after he traveled to New York City. He was stopped by authorities last Thursday, Sept. 10, while driving a rental car on the George Washington Bridge, which connects the city with New Jersey, but Zazi later returned to Colorado by airplane, his lawyer said.

Early on Monday, a joint anti-terrorism task force carried out a series of raids in an area of the Queens borough of New York where he had visited over the weekend.

Authorities revealed few details of those raids. Local media has reported that investigators sought evidence of explosives or bomb-making materials. Local officials said agents detained four members of one family, but how long they were held and their connection to the probe was not clear.

The raids rattled some residents as they came days after the anniversary of the Sept. 11, 2001 attacks.

The FBI and the U.S. Department of Homeland Security later issued an advisory to police agencies on how to track evidence of bomb-making, including looking for burn marks typically found on suspects involved in producing a particular kind of explosive device.

Zazi's father, Mohammed, a native of Afghanistan, told the Denver Post he moved to New York in 1989, and later brought his family over with him, including his Afghan-born son. The family subsequently moved to the Denver area. (Additional reporting by Edith Honan in New York; Jeremy Pelofsky in Washington; Editing by Steve Gorman and Eric Walsh)