FBI agents and police carried out a dawn raid on three apartments in New York during an investigation of a man suspected of links to Al-Qaeda.
The searches came after the man, who was under surveillance for possible links to the terror network, visited New York over the weekend and left the area.
Senator Charles Schumer of New York, who was briefed yesterday on the operation, said a terrorist attack was not believed to be imminent, and added that the law enforcement action was unrelated to President Barack Obama's visit to the city on Monday.
New York Police confirmed that searches were conducted in the borough of Queens by agents of a joint terrorism task force.
Residents described how officers armed with search warrants raided their neighbourhood at about 2.30 a.m.
Afghanistan native Akbari Amanullah said when he arrived home from work afterward, he was told that one of his roommates had been taken away.
No arrests were announced, and neither the FBI nor police would discuss the whereabouts of the Al-Qaeda suspect.