A fast-food restaurant in Lolo reported to authorities that they had received several counterfeit $20 bills in the past few days.

Missoula County Sheriff's Office spokeswoman Paige Pavalone said her office received a call from the McDonald's Restaurant in Lolo.

"According to the report, the manager said she was closing her till at the close of the night  and observed that there were several bills that looked different than all the others," Pavalone said. "When she inspected them further, she noted that one side had darker ink that the other. She borrowed a special pen that helps to identify counterfeit money from an adjacent business, and discovered the the bills were indeed counterfeit."

Because there is no surveillance video at the restaurant, the manager did not have a time frame in which the money was passed.

Pavalone said the sheriff's department has notified other businesses in the area that someone is passing counterfeit $20 bills, and to be on the lookout for the suspect. Anyone with information is asked to contact the Missoula County Sheriff's Office at 258-4810, or Crimestoppers at 721-44-44.

Counterfeiting is a federal offense that is often investigated by the United States Secret Service.