An ex-con owner of a Pennsylvania pretzel shop was arrested Thursday for allegedly selling prescription drugs through his store’s drive-through window.

Brian Schlagel, the 45-year-old owner of a Philly Pretzel Factory franchise in Monroeville, had been under surveillance from the DEA for months over suspicion that he had been distributing prescription pain pills.

The investigation started in July when police received a tip that a pretzel shop owner was purchasing pills from prescription drug users and flipping them for profit through his business.

One suspect who admitted to purchasing illicit pills from Schlagel told police that the pretzel maker was “the biggest pill dealer” in town.

Police swopped down on Schlagel after staking out the pretzel shop and watching him buy $14,000 worth of oxycodone in a parking lot near the store, cops said.

Schlagel tried to hide newly purchased pill bottle — containing 240 30mg pills of oxycodone — in an envelope full of money after being confronted by police, officials said.

He faces charges of possession with intent to deliver, prohibited acts and tampering with evidence.

Schlagel has a criminal history and an arrest record for pill usage. He also served jail time in 2016 for a hit-and-run after driving into two people on motorcycles.