From the Harford County Department of Emergency Services:
(Forest Hill, MD) – The emergency notification sirens for the Peach Bottom Power Plant in northern Harford County have activated. The Harford County Department of Emergency Services, 911 Center advises the siren activation is accidental in nature.
An investigation into the cause of the accidental emergency siren system activation is now underway. There is NO EMERGENCY at the Peach Bottom Power Plant in nearby Pennsylvania. Citizens should take no action to evacuate.
Further information will be forthcoming.