FLINT, Mich. (AP) — Officials say hacking apparently is to blame for the recent sounding of emergency warning sirens in a Michigan county.

Genesee County 911 Executive Board Director Mark Emmendorfer says the tones of the sirens Tuesday in the Flint area suggest hacking. He says the FBI and the Federal Communications Commission are involved in the case. Officials previously blamed an apparent malfunction.

It's the third time in about a month that the sirens used during for tornado warnings and civil defense emergencies went off when there was no emergency.

Emmendorfer says: "It's not funny and it's criminal. This time of year, tornado season, people may already be on edge."

A $1,000 reward is being offered for information about the case. The Genesee County sheriff's office also is part of the investigation.