WASECA — Police have arrested a 17-year-old boy after explosive devices were found on a school playground in southern Minnesota this spring.

Waseca police arrested the boy around 10:30 p.m. Tuesday after executing a search warrant at a home and a storage facility. The Bloomington bomb squad also was part of the search.

Three small explosive devices were found on the Hartley Elementary School playground in March. One was found already detonated inside a toy. A bomb squad detonated a second one and a third failed to ignite.

Police believe the small mini-bombs were homemade. No one was hurt.