The 4-year-old girl attended a party Wednesday at Huron Park Elementary in Roseville, where plastic eggs that were supposed to contain candy were distributed for an Easter egg hunt.
Police said she opened the egg at home and found the pill, a generic form of Xanax. Her mother notified school officials.
John Kment, superintendent of Roseville Community Schools, said no other parents reported finding anything unusual in the eggs and the pill was turned over to police. Kment said children brought eggs from home for the event that were taped shut.