Italian police say they have arrested two people who helped run a Milan day care center where belts were used to tie children to chairs.

Police say other children were left in dark rooms, and a toddler was bitten on the face by a female worker.

Police said Monday hidden cameras helped their investigation. Carabinieri Capt. Maurizio De Angelis said children had abuse marks and "it was impossible to think the marks were caused by play given the children's young age."

Italian news reports said that the people arrested denied wrongdoing, and that two others were under investigation. Italian news agency Ansa quoted a grandmother as saying when she asked about marks on her grandson's neck, workers told her he was tugging on his bib.