Police said witnesses reported seeing a man flee the vehicle. A smell of gasoline was reported coming from the vehicle, which was described as a U-Haul or Ryder truck.
The NYPD bomb squad and other emergency responders rushed to the scene in a city still jittery from the attempted car bomb attack in Times Square on Saturday.
Police X-rayed the truck and cut a hole in the side and discovered it was empty. They're looking to speak to the person who abandoned it. Traffic on the bridge resumed around midnight.
The Robert F. Kennedy Bridge formerly was called the Triborough Bridge. It's a complex of spans connecting Manhattan, Queens and the Bronx.