By CBSNewYork Team

PARSIPPANY, N.J. (CBSNewYork) — Investigators are trying to determine the cause of an overnight fire at a strip mall in Parsippany, New Jersey.

At least five businesses will have to be demolished.

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The fire broke out just before 1 a.m. Tuesday at the Greenhill Plaza along Parsippany Road.

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The blaze went up to three alarms, and fire departments from at least three other towns assisted in getting the flames under control.

It’s unclear exactly what caused the fire, but it is believed to have started in one of the restaurants.

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One firefighter suffered a medical issue and was taken to the hospital in stable condition.

CBSNewYork Team