Employees of a Metro East manufacturing plant were put on lockdown Friday afternoon after a threat was discovered to have been made.

Police said Olin Brass, a copper plant based in East Alton, Ill., temporarily stopped operations at their Casting, Brass Mill, and Fab and Cupping plants once a "communication" threat was discovered, prompting a lockdown. No word was immediately given regarding the context of the threat.

The situation was resolved and the plant opened back up around 3:30 p.m.

Officials are still investigating the incident.

As more information becomes available, this story will be updated.