The dealerships were ransacked and several cars stolen. One business owner said two break-ins have already cost him $50,000.
Surveillance video shows Friday night's break-in, as seven young men rushed into one of two car dealerships run by Omar Tahib.
"They're breaking into our office and trying to find any keys we have laying around hoping that it goes to one of the cars we have out in front so they can drive off in it," he said.
Tahib has resorted to taping signs on his window to warn any future burglars that a break-in would be useless. The signs read: "No keys in this location during night time."
He's already lost more than $50,000, including a totaled Fiat 500 that was stolen during a break-in on March 1. It was found on Monday.
"All of the cars seem to be recovered in Oakland or somewhere in Oakland," Tahib said. "Like this one was recovered on the highway, but in Oakland. The CHP had picked it up."
Just a few doors down, the front window was smashed at Phantom Motors. Burglars made off with several keys and a few cars.
"They're skilled, they know what they're doing," said Ken Zemari with Phantom Motors. "They were successful, they were able to take a couple of Mercedes Benz."
A total of three used car dealerships were broken into on Thornton Avenue.
A fourth on Decoto Road was also hit. Workers there were busy Saturday night repositioning a truck to block their driveway in an attempt to prevent anyone from using keys stolen during Friday night's break-in.
Police are combing through surveillance video to see if they can identify the seven young men.
Until they're caught, Tahib has some advice for other car dealerships.
"I suggest other dealerships in the area to not leave their keys on site anymore overnight because obviously these juveniles really don't care," he said.
Tahib will also be installing more surveillance cameras.