Chicago police have arrested more than a dozen people for ripping off luxury cars from the rental app Car2Go. CBS Chicago reporter Brad Edwards tweeted the news this afternoon, stating that as many as 100 pricey Mercedes-Benz cars went missing after a “hack” — a number Car2Go confirms, though the company says the problem is fraud, not a security breach. We still don’t know how the cars were stolen, but the problem is supposedly limited to Chicago, and local police say they’re working “across several districts” to recover the 100 wayward vehicles.

Car2Go was founded by German car manufacturer Daimler, and members can use an app to rent a super-compact Smart car or a Mercedes-Benz — but suspects apparently targeted the latter. Edwards also wrote that many of the cars were being “used for crimes,” and that more than 12 people were in custody for the thefts. Chicago police later told The Verge that 16 people had been brought in for questioning.

We are working with law enforcement to neutralize a fraud issue. No personal or confidential member information has been compromised. As a precaution, we are temporarily pausing our Chicago service. We will provide an update as soon as possible. Apologies for the inconvenience. — car2go Chicago joins SHARE NOW (@car2goChicago) April 17, 2019

“We were alerted by a car rental company that some of their vehicles may have been rented by deceptive or fraudulent means through a mobile app. Due to the information provided by the company, numerous vehicles have been recovered and persons of interest are being questioned,” a police spokesperson told The Verge. “We are working with the company to determine whether there are any other vehicles whose locations cannot be accounted for. At this time, the recoveries appear to be isolated to the West Side. The investigation is ongoing.”

Police said they couldn’t confirm a final count of arrests or stolen vehicles. In a tweet, Car2Go said it was “temporarily pausing” its service in Chicago.

Car2Go — which merged with BMW service DriveNow in February, adopting the name Share Now — was adamant that this shouldn’t cause alarm for users. “Clarification: We were not hacked,” the company tweeted. “This is an instance of fraud, isolated to Chicago, and we are currently working with law enforcement. None of our member’s personal or confidential information has been compromised. No other Share Now North American market has been affected.”

High-tech modern cars can be vulnerable to hacking, but these thefts are likely more mundane. In 2012, for instance, a ring of criminals stole four high-end vehicles from luxury car-sharing startup HiGear — using fake identities and credit cards to sign up and pay for the cars.

Update, 7:22 PM ET: Car2Go confirms that the Chicago Police Department is looking for 100 missing Mercedes-Benz cars.