It happened around 1:27 p.m. at 713 George Street.
Officers say the children, ages two, three, and four, had been in a room watching television with their mother. They say the mother was asleep when one of the children gained access to a candy Ice Breakers container.
The container was holding several prescription grade pills. Police say the children were able to open the container and ingest the prescription medication inside.
Police say all three children were transported to Meritus Medical Center for treatment.
Hagerstown detectives are continuing to investigate this incident.