The incident was reported after a man left his car unlocked with his daughter inside while he went into a 7-Eleven on Bay Shore Road on Friday morning.
While the father was inside, a man pulled up in a red van and drove away with the car while the child was inside.
The child was dropped off in the parking lot of West Islip Hot Bagels a short time later and was not injured.
The suspect then drove away in the car.
Detectives are asking anyone with information on this incident to call the First Squad at 631-854-8152 or call anonymously to Crime Stoppers at 1-800-220-TIPS.
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