FALMOUTH, Maine — Several counterfeit bills have turned up at local businesses, but police are confident the case will be solved.

The phony $20 bills were discovered on six occasions at four stores — Goodwill, Walmart and both Dunkin’ Donuts locations, Lt. John Kilbride said.

“We started getting the funny money last week, right around the 20th,” he said. “We’re actively working the case. Hopefully we’ll have a resolution down the road. I like the way the case is progressing.”

The police department is “in counsel” with the U.S. Secret Service — the agency that handles major counterfeiting cases — but due to the relatively small number of the bills, the case will be handled by Falmouth police, Kilbride said.

Stores should use special pens to check for counterfeit bills and train employees how to handle suspicious transactions, according to Kilbride.

“If you’re questioning the money, make note of who you’re getting it from, the time, date, plate number,” he said.