At approximately 1:19 pm this afternoon, the Three Mile Island (TMI) warning siren located at 2nd and Hanover Streets in the Borough of Hummelstown inadvertently sounded an alert for a duration of less than 30 seconds.  Dauphin County Emergency Management Agency (DEMA) received notice of the sounding through an automated monitoring network and has coordinated with officials of Exelon, the operator of TMI, to determine the cause of the alarm’s inadvertent sounding. 

Siren maintenance personnel from Exelon responded immediately and are continuing efforts to identify the cause of the alarm sounding.  They will repair or replace any components necessary to ensure the siren works as designed. 

There are 96 warning sirens within the Emergency Planning Zone (EPZ), a 10 mile radius surrounding TMI, throughout portions of Cumberland, Dauphin, Lancaster, Lebanon and York Counties.  Exelon plans to replace all 96 sirens within the EPZ later this year with newer, louder sirens, each with a battery back-up power source.  Additionally the control and monitoring systems for the sirens will be replaced with improved technology.