Several packages containing a "suspicious" substance have been sent to sites near the stadium where the Super Bowl will be played on Sunday.
However, New Jersey State Police said no injuries were reported.
Local media said the packages were sent to sites including six hotels and the office of former New York Mayor Rudolph Giuliani in Manhattan.
Mr Giuliani's office has not responded to the reports.
The Econo Lodge hotel in Carlstadt, New Jersey, said it received an envelope containing a loose white powder.
Hotel manager Eylem Naik said authorities had tested the powder and pronounced it harmless.
New York and New Jersey police have been out in force throughout the metropolitan area ahead of the NFL championship game.
Met Life Stadium in East Rutherford, New Jersey, about 16km west of New York City, has been on lockdown since Sunday.
Both teams, the Denver Broncos and Seattle Seahawks, have been staying at hotels in Jersey City in the week leading up to the game.