ST. LOUIS COUNTY, Mo. – An anonymous threat has caused Mehlville High School to lock down Monday.

The Mehlville School District said as of 12:30 p.m., police were at the school investigating. They assured all parents that all students and staff are safe. The lockdown was lifted at approximately 1:40 p.m.

The district said all “students remain locked in their classrooms or other safe location” during a lockdown. No one is allowed to enter or exit the school at this time until the police give an all clear. They ask parents to not come to the school to pick up their children.

An update will be sent out shortly. FOX 2 will continue to update this story with more information as it becomes available.