South River Middle and Elementary school students were evacuated Friday after a student found ammunition in the middle school, authorities said.

According to South River schools superintendent Ronald Grygo, school authorities allegedly received a call Thursday evening from a student who said that "there might be cause for concern."

After the ammunition was discovered the middle school was locked down at 12:30 pm to allow police, fire, rescue squads and K-9 units worked to determine the cause and extent of the threat.

Authorities searched the building with dogs for two hours before declaring the building safe and allowing students to re-enter.

A statement was sent to parents Friday afternoon assuring them that there was no threat to the students, staff or buildings, and thanking them for their cooperation.

The investigation is ongoing.