The storm, which blew ashore as a fierce Category 4 hurricane, packing sustained winds of 155 mph, is so far being blamed for two fatalities.

Florida National Guard personnel on storm duty Thursday numbered about 2,250 and up to 3,500 troops have been authorized, according to the National Guard Bureau.

The Florida National Guard has started search-and-rescue operations and has mobilized logistical support, boat teams, transportation and aviation support.

Guard units in the region -- Alabama, Georgia, North Carolina and South Carolina -- may be mobilized as needed.

Air Force Gen. Terrence J. O'Shaughnessy, the commander of North American Aerospace Defense Command and U.S. Northern Command, briefed reporters Wednesday at the Pentagon on the Defense Department's preparations to support the Federal Emergency Management Agency in the states affected by Hurricane Michael, which has been downgraded to a tropical storm.

"We are surrounding the storm," O'Shaughnessy said. "This is no small feat given the unprecedented size and strength of [Hurricane] Michael."

Before the hurricane even made landfall, 2,216 active-duty personnel were in position, along with 32 helicopters, 240 high-water vehicles and 32 swift-water boats.

Although Florida has endured many hurricanes in the past and has a robust capability for dealing with the storms, the federal government assists as part of the national response framework, O'Shaughnessy said.

The Defense Department's preparations and efforts to support the Federal Emergency Management Agency and disaster relief efforts across states affected by Hurricane Michael are coordinated through North American Aerospace Defense Command and U.S. Northern Command.

Contributing: Steve Marshall of the National Guard Bureau