At 12:15 p.m. Thursday, all 96 emergency notification sirens in the 10-mile radius around Three Mile Island Nuclear Generating Station will be sounded for three minutes, Exelon Nuclear announced. TMI must sound its sirens for a full three-minute test once a year, the company said. TMI conducts routine electronic testing of the sirens on a weekly basis.

York, Cumberland, Dauphin, Lancaster and Lebanon counties will activate the sirens from their county 911 Communications Centers. Personnel from TMI cannot sound the sirens; only county emergency management officials have the capability and authority to do so.

The sirens are used to notify residents to tune into an Emergency Alert System (EAS) radio or television station in case of an emergency at TMI or tornadoes, floods or other events requiring notification to residents.