A school-safety agent who found two gift cards and kept them prompted an NYPD Internal Affairs Bureau probe and has now been arrested, police said Friday.

Gregory Nelson, 60, an NYPD employee at MS 390 in The Bronx, allegedly found the gift cards during his shift at the school, police said.

Instead of returning the cards, police said, Nelson spent them, prompting an IAB investigation.

Nelson was arrested Thursday at 5:22 p.m. and charged with criminal possession of stolen property, cops said.