The accident happened around 1:30 a.m. Tuesday in the southbound lanes of the Turnpike between Exits 8A and 8 in Hightstown, Mercer County.
The UPS tractor-trailer burst into flames after colliding with the box truck. Officials say it took over an hour for fire crews to get the flames under control.
Traffic was jammed for roughly 6 hours approaching the accident scene. Crews have since moved much of the wreckage onto a nearby construction area and traffic is now getting by.
There is no word on the identity of the person killed in the crash.