ST. JOHNS COUNTY, Fla. -

Deputies in St. Johns County are investigating after they said someone used counterfeit money at a school book fair.

It happened Thursday at Otis Mason Elementary School off Mason Manatee Way.

Deputies said an employee at the school was counting money from the event when she came across a bill that felt "different" from the rest of the money.

Investigators said the employee swiped the bill with a counterfeit marker, and sure enough it was fake.

Deputies said it was a fake $10 bill, which qualifies as a third-degree felony.

Anyone with any information about the case is asked to call Crime Stoppers at 888-277-TIPS.