The NYPD bomb squad inspected the vehicle and gave the 'all clear,' said NYPD Deputy Commissioner Paul Browne.
A police vehicle equipped with x-ray equipment inspected the truck and found nothing inside. Police also cut a hole in the shell of the truck to look inside and also found nothing of concern.
The incident began at 9:40 PM when a bridge toll operator saw a man run away from the truck and towards Queens. The operator then went towards the vehicle and smelled gas. That operator called police, according to Browne.
It is not known why the man ran away from the scene, Browne told nbcnewyork.com.
The vehicle was left on a ramp leading from the Bronx section of the Bruckner Expressway heading to Manhattan and Queens. NYPD and Triborough Bridge and Tunnel Authority officers were on scene to try to redirect traffic as the investigation was ongoing. The fire department was also called to the scene as a precaution.
The concern over the abandoned U-Haul truck, which had Arizona plates, comes amid the ongoing Times Square car bomb investigation.
Officials stressed closing the bridge to traffic for more than an hour was a precaution.