According to police, the thieves will break into the State Highway Department in Cherry Hill to steal valuable equipment and metal that can be sold for scrap.
They're using heavy rigs to make their getaway.
Lt. William Kushina of the Cherry Hill Police Department said, on two occasions, the thieves used a front-end loader to load the heaviest stuff that they're stealing on to the back of a dump truck.
"They then drove the dump truck through the fence and out," said Lt. Kushina.
On New Year's Eve, the thieves got away with a pallet of 200 batteries worth $26,000. They're specialized batteries used for powering temporary highway signs.
Once again they used a state dump truck.
"On two occasions they've used the stolen dump trucks and take the stolen property to wherever they're taking it and then return the trucks back to the yard," said Lt. Kushina.
The last time, a supervisor spotted the truck returning to the yard at 5:00 a.m. He tried to follow but the thief abandoned the truck along Route 70 and took off into the woods.
The yard has been hit four times since August and police estimate the thieves have gotten away with tens of thousands of dollars worth of state property.
Police think the suspects are taking the loot to a hidden location for storage before they try to sell it as scrap.
They seem to know where to find the valuable stuff.
"Sounds like they have some information about what's going on," Lt. Kushina said. When asked if it might be an inside job, Lt. Kushina said "It's a possibility. We have to look at everything."