ST. JOSEPH, Mo. -- Parents were still reeling in St. Joseph on Thursday after a shocking morning Wednesday involving Spring Garden Middle School students.

Seven students – all girls – were rushed to a hospital after overdosing on a prescription drug.

St. Joseph police said the girls took the drug methadone, a pain reliever that’s used to treat drug addiction.

Police said they believed the girls got the drug from a friend who got it from a 16-year-old high school student.

Police arrested that teenager, but they were still trying to sort out where she got the drug.

"We have heard about methadone being misused, but this is the first time we have seen it in schools like this where it's been students who've been affected by it," said Sgt. Kevin Castle of the St. Joseph, Mo., Police Department.

A St. Joseph mother was "terrified" by the incident.

"I have two children getting ready to go to middle school and to know that that is in our city and is going around our schools, it just absolutely terrifies me," Shablix Jones said. "My heart is just racing knowing that is here and it's going it around. It can kill the children."

All of the students were expected to be OK, but an emergency room physician said methadone was an effective drug when used properly but an overdose could be deadly.

Dr. Pamela Ramsey said, "If they took it, you don't catch them, the next thing is you may be walking in trying to wake up a child that doesn't wake up, every parent's nightmare."