A Colorado man whose visit to New York apparently set off government raids on severalQueens apartments on Monday has denied having ties to al Qaeda or any other terrorist group.

“I have nothing to do with this,” said the man, Najibullah Zazi, 25, who was reached by telephone in Colorado on Monday and Tuesday. “This looks like it’s going toward me, which is more shocking every hour.”

Law enforcement authorities have not divulged the man’s identity, but they confirmed that he was suspected of having al Qaeda ties and was already under surveillance for that reason.

The man whom officials were watching left New York last weekend, according to officials who have knowledge of the raids but were not authorized to discuss them. No arrests were made and no explosives or weapons were found.

Representative Peter T. King of Long Island said agents of the city’s Joint Terrorism Task Force “acted very appropriately” in carrying out the raids.

“It was based on the totality of the evidence, and from what I understand of the evidence, it was important that they acted when they did,” Mr. King said. “I am positive they did the right thing.”

Federal authorities regarded the man to be a legitimate terrorist suspect who had become the focus of intense investigation and elaborate covert surveillance before his trip to New York, according to government officials briefed on the case.

The man’s arrival last Thursday appeared to be the event that prompted authorities to stop his car near the George Washington Bridge and then carry out the searches that began late Sunday night — based on federal search warrants drafted during a frantic weekend in which prosecutors in New York and Washington hastily assembled the necessary legal documents. Officials said they decided to disrupt any plot that might have been imminent, but the raid came before investigators understood the suspect’s intentions, according to several federal officials. Because there were no arrests, officials have been left to assert that they acted out of an abundance of caution.

But several said the raids were carried out well before investigators had a prosecutable case, and before they had figured out the nature of the plot, its intended target or its likely means of execution — if there was a plot at all.

Several federal officials said they were persuaded that the case was an important one and had been moving in a significant direction, but was prematurely brought to a close at the urging of police officials in New York.

Mr. Zazi said on Tuesday that he was contacting a lawyer, but he invited theF.B.I. to question him.

“I was hoping they’d come question me, give me a chance to question them, ask, ‘Why are you following me?’ ” said Mr. Zazi. “If they want to investigate, they can.”

He said he left Aurora, Colo., in a rented car and headed to New York to try to resolve an issue with a coffee cart that he said his family is licensed to operate in Lower Manhattan. A spokeswoman for the New York City health department could not confirm if the man or his father operated a mobile food cart.

Mr. Zazi said he was stopped at the George Washington Bridge by the authorities, who briefly detained him and searched his car. A city official confirmed that officers stopped a man at the bridge and searched his car, and that “everything was clean.” The official could not say what prompted the stop.

Mr. Zazi said he thought the police might be profiling him or suspected him because he has a beard and had rented the car. The next day, he said he thought his car had been stolen, but the police told him it had been towed. The following day, he said, he noticed he was being followed and called the police twice to complain.

Finally, he said, he cut short his stay in New York, deciding to fly back to Colorado on Saturday.

“It was too much for me,” Mr. Zazi said. “I said, ‘I can’t stay here, even for a minute.’ ”

A relative of Mr. Zazi’s who lives in Aurora, Colo., Abdul Jaji, said he has “never seen anything wrong” with Mr. Zazi, and that he works 16-hour days as an airport shuttle driver. He added that Mr. Zazi traveled last year to Peshawar, Pakistan, where his wife lives, and stayed there four months.

It was not known who ordered the searches, but it was evident that that decision worsened the sometimes-quarrelsome relations between the New York Police Department and the F.B.I.

Evidence uncovered as part of the investigation and raids prompted the F.B.I. and theDepartment of Homeland Security to issue a bulletin to law enforcement agencies around the country, warning them to be vigilant about homemade explosives, officials said.

The bulletin said the two agencies had no specific information on the timing, location, or target of any planned attack. But it noted that chemicals used to form hydrogen-peroxide-based explosives can be found at places like hardware stores and pharmacies, and that recipes for such explosives are easily obtainable.

Police CommissionerRaymond W. Kelly said Tuesday that while “there was enough substance” in the intelligence gathered to result in search warrants for the raids, the city was not under an imminent threat.

At one raid site, a fifth-floor apartment on 41st Avenue, a tenant, Naiz Khan, spoke of Mr. Zazi, who stayed overnight there on Thursday. He said that he had barely spoken with Mr. Zazi on his recent visit but that they had been closer when they were students at Flushing High School. He said he was committed to helping the F.B.I.

“Anything they need, I will help them out,” Mr. Khan said on Tuesday, standing amid a messy jumble of belongings. “It’s my responsibility.”