US investigators probing the attempted bombing in New York's Times Square have arrested three men during searches of homes in New York, Boston and Philadelphia.
Justice department spokesman Dean Boyd said the men were being held over alleged immigration violations.
US Attorney-General Eric Holder has described the arrests as a significant step in investigations into the failed car bomb attack.
Mr Holder says those detained were connected with the only person arrested so far over the attempted bombing earlier this month.
Pakistani-born US citizen Faisal Shazhad, 30, has already been charged with the attempted bombing on 1 May, when a car containing a crude bomb was found parked in the busy New York neighborhood.
Another suspicious vehicle investigated
New York City police were forced to clear several blocks near Union Square to investigate a suspicious vehicle on Thursday, but say it appears there is no danger.
Police say the vehicle was parked in front of the Con Edison headquarters and had what appeared to be two gas canisters visible in the rear.
The owner of the car has been found.