NEW YORK (CBSNewYork) — Authorities are searching for the driver behind a deadly hit-and-run after a man was struck and killed while walking along the Cross Bronx Expressway early Sunday morning.

Police say they received calls of a pedestrian struck on the heavily traveled thoroughfare just before 2:30 a.m.

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Upon arrival, authorities discovered an unidentified adult male laying unresponsive across the road. Medics arrived and pronounced the victim dead at the scene.

Investigators have determined that the man was walking along the northbound side of the expressway between the Castle Hill Avenue and White Plains Road exists in Parkchester when he was struck by an unknown number of vehicles — none of which remained at the scene.

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The roadway remained closed for several hours as authorities conducted their initial investigation.

Police are having trouble determining exactly how many times the victim was hit since his body is so badly mangled.

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The NYPD’s Highway Collision Squad has taken over the investigation, which is ongoing.