Arlington middle school placed on lockdown after threat reported; police continuing to investigate

An Arlington middle school was placed on lockdown while police investigated a written threat.

Police say Gunston Middle School in Arlington was secured by police following the report of the threat. 

The school conducted a controlled dismissal and police remained on scene to assist. They say the process is complete and all students are safe.

The investigation into the credibility of the threat is ongoing.

This is a developing story. Check back with FOX 5 for updates.