Workers at a Maine restaurant were stunned Friday after they opened what they thought was a shipment of new mugs only to find roughly $3 million worth of fentanyl.

The incident at Mac's Grill in Auburn occurred after employees cracked open a wooden crate they believed the mugs were in, according to a report.

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Instead of new mugs, the employees found at least 31 pounds of fentanyl packed into bricks, the Auburn Police Department said.

The shipment originated in Arizona, and the name on the shipping label read "Jeremy Mercier."

No one at Mac's went under that name, but a man arrived at the location hours later, stating he had a package waiting for him.

Restaurant staff had already alerted the police, and the 41-year-old Mercier was arrested.

Authorities seized the fentanyl and $2,780 Mercier had on his person.

"I am glad that this fentanyl didn't make its way to the 'street,'" Mac's owner Mike Peters said.

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"The instances of overdose in our, and surrounding, communities is awful, and fentanyl seems to be front and center when it comes to fatalities. It is very sad."

An investigation into the incident is ongoing, according to Auburn Deputy Chief Tim Cougle.