By Matt Petrillo

DELAWARE COUNTY, Pa. (CBS) — Throngs of dirt bikes, ATV, and other types of off-road vehicles flooded parts of Radnor this weekend – and authorities want to find out where exactly they all came from.

In dash cam video exclusively obtained by Eyewitness News, police found the large group riding the wrong way down Lancaster Avenue near Villanova. The clan even went through a red light.

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The intimidating sight is a first for the Main Line. Residents were taken aback by the crowd and noise.

“It was definitely alarming,” Villanova student Halina Takahashi told CBS3. “It was so loud.”

Costa Xinos of Nova Mediterranean Grill, caught video of riders doing tricks in traffic and said it was between 200 and 300 riders, some looking as young as teenagers.

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“There was a group of young ladies that was coming from Starbucks, and they got scared so they took refuge right in the store,” he said.

Radnor Police didn’t issue citations Saturday, focusing on clearing out the riders instead. Superintendent Christopher Flanagan said it was to prioritize safety.

“The last thing we want to do is have a high-speed incident,” he said, adding, “Officers tried to block intersections so they could go through without anybody getting hurt.”

The initial thought is the riders came from Lower Merion, something their law enforcement is looking into as well. Eyewitness News caught video of a large group of ATVs and dirt bikes on Kelly Drive in Philadelphia Saturday. The investigation is ongoing, but none of the riders had license plates.

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Radnor Police issued a safety alert Monday telling drivers to not engage with riders.