NEW YORK — Counterterrorism officials are warning police departments around the country to be on the lookout for evidence of homemade bombs following raids on several New York City apartments in a hunt for explosives and possible links to al-Qaida operatives.
Investigators issued warrants to search the residences early Monday for explosives material but did not find any, according to a person briefed on the matter who was not authorized to discuss the case and requested anonymity.
The searches came after the man, who was under surveillance for possible links to the terrorism network, visited New York City over the weekend and then left the area, said Rep. Peter King, R-N.Y.
The joint FBI and Homeland Security intelligence warning, issued Monday, lists indicators that could tip off police to homemade hydrogen peroxide-based explosives, such as people with burn marks on their hands, face or arms; foul odors coming from a room or building; and large industrial fans or multiple window fans. The warning, obtained by The Associated Press, also said that these homemade explosive materials can be hidden in backpacks, suitcases or plastic containers.
The notice was not intended for the public, said Justice Department spokesman Richard Kolko.
Homeland Security and the FBI have no specific information on the timing or target of any planned attack, Kolko said, but "we believe it is prudent to share information with our state and local partners about the variety of domestically available materials that could be used to create homemade explosives, which have been utilized in previous terrorist attacks."
Sen. Charles Schumer said the law enforcement action Monday was unrelated to President Barack Obama's visit to the city the same day.
"There was nothing imminent, and they are very good now at tracking potentially dangerous actions, and this was preventive," said Schumer, D-N.Y.
Both lawmakers were briefed by law enforcement officials.
Two U.S. intelligence officials, who requested anonymity because they were not authorized to discuss the case publicly, said the target of any purported attack - or who would carry it out - remained unclear.
Authorities have not found any weapons ready for use that would indicate an attack was imminent, they said. Nevertheless, one of the officials called the threat very real and emphasized the urgency of it.
New York Police Department spokesman Paul Browne confirmed that searches were conducted in the borough of Queens by agents of a joint terrorism task force.
Residents in the Flushing neighborhood of Queens on Monday described officers armed with search warrants swarming their immigrant neighborhood at about 2:30 a.m.
Akbari Amanullah, a cab driver who lived in an apartment with four other natives of Afghanistan, said when he arrived home from work afterward, he was told that one of his roommates had been taken away.
Neither the FBI nor the NYPD would discuss the whereabouts of the al-Qaida suspect or whether anyone was being held for questioning in New York.
A White House spokesman said Obama, who spoke on Wall Street on Monday, had been briefed on the investigation.
The person familiar with the case said the raids were the result of previous law enforcement surveillance of people.
The investigation was continuing.
One man at a three-story brick apartment building in the neighborhood confirmed Monday that authorities had been at his apartment, but he wouldn't identify himself or comment further. Nearby resident Kabir Islam said he saw FBI agents and police officers surrounding the apartment when he arrived home after 3 a.m.
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Amanullah said about a dozen FBI agents went to his nearby fifth-floor apartment at about 2:30 a.m.