Three Mile Island's new emergency notification siren system failed to sound during a scheduled test Thursday afternoon.
The original siren system passed the first of two tests at 12:15 p.m., but Exelon spokesman Ralph DeSantis said none of the 96 upgraded sirens sounded during a second test at 1:15 p.m.
The problem was later linked to a control box wasn't upgraded properly.
"A certain upgrade was going to be done and was not completed before the test," Exelon spokesman Ralph DeSantis said. "It looks like it was an issue between us and the manufacturer really not communicating properly and making sure that upgrade was completed."
All 96 sirens around the nuclear power plant were supposed to sound for three minutes during each test.
The new system has a battery backup capability that allows the sirens to sound during power outages.
Exelon needs FEMA approval to put the new system into place, and the testing is part of that process.
A full three-minute sounding of the sirens is required on an annual basis.
The purpose of the sirens is to notify residents to tune into an Emergency Alert System radio or television station in case of an emergency.