PENNINGTON, N.J. (CBS) — Police in New Jersey are investigating a freak accident that killed the driver of a tractor-trailer Tuesday morning.

The tragic accident happened on Route 31 at West Delaware Avenue in Pennington, Mercer County.

According to investigators, a flat-bed tractor-trailer was hauling long beams of structural steel when the weight shifted, sending the beams into the cab of the tractor-trailer. Authorities say the driver of the tractor-trailer was struck by the steel and was killed.

The identity of the driver was not immediately released.

Route 31 was shut down for some time as police investigated the incident.

The deadly accident remains under investigation.

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