SPRING CITY, TN (WRCB) -- The Nuclear Regulatory Commission and the Tennessee Valley Authority are investigating a shooting on TVA property near the Watts Bar plant.

Officials say a security guard patrolling on TVA property exchanged gunfire with someone around 2 a.m.

TVA spokesperson Jim Hopson says the officer was patrolling when he encountered the individual. When the officer asked the person what they were doing there, the individual fired shots at the officer.

The officer returned fire and when he went to call for backup, the individual fled.

At least one round struck the officer's vehicle. The officer was not injured.

The area where the incident occurred is outside the plant's protected area and the plant remains secure.

As a result of the incident, the Watts Bar plant staff declared an unusual event, the lowest of the NRC's four emergency classifications.

Staff confirmed there was no lapse in security measures and exited the unusual event status at 12:30 p.m.

The NRC has staffed its incident response center in the Region II office in Atlanta and is monitoring the events along with the resident inspector who has responded to the site.

The FBI, Rhea County Sheriff's Department and Meigs County Sheriff's Department are assisting with the investigation.