The Y-12 National Security Complex in Oak Ridge has reopened after a "security situation" this morning.
Earlier today the complex posted a notification saying it had closed all entrances as it responded to a law enforcement matter.
"The facility and its employees are safe and secure," a post on the Y-12 Facebook page read.
Y-12 says its officials are working closely with the City of Oak Ridge Police Department on the matter.
This is a developing story. Stay with the Times Free Press for updates.