MARQUETTE, Mich. (AP) -- No, zombies aren't attacking northern Michigan.

Two local television stations say hackers broke into their Emergency Alert System with messages Monday warning of a zombie apocalypse. Along with a crawl strip, an audio message warned viewers that "dead bodies are rising from their graves" and "attacking the living."

The messages ran on public station WNMU and ABC affiliate WBUP. Two Montana stations also were hit.

WNMU General Manger Eric Smith says police determined the source isn't local and may be from outside the country. He wasn't aware of any arrests and says equipment changes have been made to prevent future incidents.

Karole White, president of the Michigan Association of Broadcasters, says it's the first breach of the emergency system that she's aware of since its inception in the 1940s.