CAMDEN, N.J. (CBSNewYork/AP) — A massive search is underway after two undercover police officers were shot while sitting in their unmarked vehicle in Camden Tuesday night in what authorities are calling an ambush attack.

It happened around 8:30 p.m. after the car stopped at a red light. At least one suspect opened fire on the plainclothes detectives, said Camden County Police Chief J. Scott Thomson.

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“The information we have thus far is that they were essentially ambushed,” Thomson told reporters at a late night news conference. “A male walked up and began opening fire. We have anywhere between 10 and 25 rounds that were fired at the officers.”

One of the detectives was able to return fire, Thomson said, but it was not immediately clear if anyone else was shot. Thomson said his department was in communication with hospitals in the region.

The detectives were taken to an area hospital and are expected to survive. One was shot in the hand and the other was shot in the arm.

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“At this point in time our officers have non-life-threatening injuries but not for the grace of God quite frankly,” Thomson said. “The amount of rounds that were fired at close range and particularly through the windshield.”

Police continue to search for the suspect or suspects involved in the “unprovoked” attack.

“Maybe they did know they were police officers and that’s the reason why they did it. Maybe they thought they were somebody else. We’ll find that out as the investigation unfolds,” Thomson said.

The shooting occurred on National Night Out, an event designed to bring local police and the communities they serve together.

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(© Copyright 2018 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)