Sirens in the Huntersville neighborhood near Duke Energy's McGuire Nuclear Station caused concerns for homeowners Thursday morning.
A Duke spokesperson said the alert was a mistake and it took them hours to figure out what triggered the sirens.
Craig Westman went on a walk with his dog through his neighborhood near Birkdale Village when he heard the alarm. Westman said he wasn't alarmed since siren testing happens often, but the timing did throw him off.
"The sirens usually go off around noon," said Westman.
At about 4:30 a.m. Thursday, crews at McGuire Nuclear Station off Highway 73 noticed a system that controls the sirens in Mecklenburg County wasn't working properly. Duke Energy spokesperson Jennifer Jabon said when crews tested the system around 10:30 a.m. and the sirens sounded.
"It was during us troubleshooting and testing. It should have been sounded silently but the test was audible," said Jabon.
For hours, crews worked to figure out what was wrong and used a backup system to activate the sirens in case an emergency happened.
They eventually found it was a communication failure in the system and fixed it about six hours after the false alarm.
"We regret that this caused any concern or inconvenience for the public," said Jabon.
Duke Energy performs a silent test on the sirens twice a week. They do an audible test once every three months. Dates for the audible tests are listed in a calendar mailed to area residents each year. Media alerts are also sent out before each test and details are available online.