Boone County officials believe the City of Rolla's emergency sirens caused the county's sirens to active two hours early.
The county normally tests its outdoor emergency sirens on the first Wednesday of the month at noon. Sirens sounded around 10 a.m. Wednesday.
The Office of Emergency Management said the activation was "not intentional."
Officials say Rolla activated its sirens on the same frequency this morning. The signal was strong enough that Boone County emergency officials heard the radio traffic and sounded the sirens.
The sirens were activated again at noon.