School bus drivers, attendants and other co-workers were charged by federal prosecutors Thursday with taking part in an illegal drug ring involving the powerful painkiller OxyContin.

According to the indictment, Miami-Dade school employees were among 29 people who used more than 100 forged or fraudulent prescriptions to obtain thousands of tablets of OxyContin from South Florida pharmacies.

No teachers were involved, and there was no evidence of drug sales to children, U.S. Attorney R. Alexander Acosta said.