A total of eight 2018 Ram 1500 pickup trucks were stolen from a factory lot in Warren, Michigan early Thursday morning, and the case has left police in the area perplexed. So far, two of the trucks have been recovered, after they were left abandoned on the streets of Detroit. One of the two ran out of fuel, but the other was apparently left driveable and undamaged.

The thefts were conducted at around 4 am last Thursday, the Detroit Free Press reports. The thieves rode up to FCA’s Warren Truck Assembly plant in a 2003 Ram 1500 that was stolen from a Warren residence, cut a hole in the chain link fence around the factory lot, gained entry to and started eight 2018 Ram pickups, and drove off through a gate at the lot’s entrance. Police were provided with vehicle identification numbers for the eight stolen trucks by Fiat Chrysler on Friday, but they lack surveillance video from the lot.

The police are hoping to acquire surveillance video from the night in question from surrounding businesses, and they’ve offered a $1,000 reward for any information that leads them to making an arrest.

Because of how well-orchestrated the thefts appear to have been, police consider it likely that the eight Ram 1500 trucks were stolen with help from a current or former Fiat Chrysler employee. “They knew where they were going, what they were looking for, what area to cut the fence and get into the lot where vehicles were parked,” Warren Police Commissioner Bill Dwyer told the Free Press. “This was not a random, all-of-a-sudden thought or idea. It was well-planned for probably several weeks.”

FCA spokesperson Jodi Tinson says that the automaker “is working with the Warren Police Department regarding the theft of [the] Ram Trucks… The company will be assessing security measures at the location and implementing any necessary changes to prevent future incidents.”