The Coast Guard issued a Safety Marine Information Broadcast (SMIB) establishing a one nautical mile security zone around the Mackinac Bridge after Michigan State Police confirmed an active bomb threat.
At approximately 2:15 p.m. EST, the Mackinac Bridge Authority closed the Mackinac Bridge after being notified of a bomb threat. Taking immediate action, the Coast Guard diverted a Station St. Ignace response boat to the area and issued an SMIB. The Coast Guard instructed transiting commercial vessels to anchor while local law enforcement executed multiple sweeps of the bridge surface and the Station St. Ignace response boat and local law enforcement marine units conducted sweeps underneath.
After Coast Guard and local law enforcement completed multiple sweeps above and below the bridge, the Mackinac County Emergency Director issued the all clear and the Coast Guard terminated the security zone.