LAKEVILLE, Minn. (AP) — Authorities are investigating after multiple Lakeville dog owners have reported finding harmful items hidden in food.

The residents believe someone is intentionally trying to harm their animals. They tell police they've found nails and screws concealed in pieces of hot dogs in their yards. They say balls of steel wool also have been found with suspicious capsules inside.

One woman says 11 screws and three open safety pins were surgically removed from her two small dogs after they were hospitalized Saturday evening. She says she'll likely be hit with a $3,000 veterinarian bill.

Another woman has been going door-to-door warning neighbors after her son found one of the potentially harmful treats while on a walk with the family dog.

Lakeville police are treating the case as a criminal investigation.