By Steve Beck, Al Novack

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PHILADELPHIA (CBS) — Investigators are probing what caused a freight train to derail in Philadelphia early Friday morning.

The derailment happened at about 3:30 a.m. on the CSX tracks near 22nd Street and Hunting Park Avenue in the city’s Tioga-Nicetown section.

Chopper 3 HD was over the scene where it showed four empty freight cars that derailed and ended up on their sides.

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Authorities tell CBS Philly that the freight cars do not contain any hazardous materials.

There were no reports of any injuries.

The exact cause of the derailment remains under investigation.

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