A devastating storm system moved across the United States on Friday, spawning a slew of tornadoes that contributed to at least 28 fatalities in Indiana, Kentucky and Ohio.

National Weather Service meteorologist John Gordon reported Friday afternoon the agency had about "half a dozen reports of tornadoes on the ground," as well as reports of "significant damage" -- making his comments before some of the worst twisters were reported.

"This is an enormous outbreak that's going on right now across Kentucky and the South," Gordon said. "It's crazy. It's just nuts right here."

Southern Indiana was particularly hard hit, with Indiana Department of Homeland Security spokesman John Erickson saying three had died in Jefferson County as a result. Sgt. Rod Russell with the Indiana State Police said later that three people also were killed in Scott County.

In addition, Emergency Management Director Leslie Cavanaugh of Clark County -- which has about 110,000 people -- reported one death. Sheriff's Department Maj. Chuck Adams added that a man was found dead in his car several miles outside Henryville.

"We've got total devastation in the north-ceindntral part of the county (and) widespread damage from the west to the east," added Adams. "We are inundated with calls."

At least 15 people were killed across Indiana, authorities said.

Aerial footage from CNN affiliate WLKY showed structures torn to shreds and large swaths of trees knocked down in Henryville, about 20 miles north of Louisville, Kentucky.

Other aerial images showed similar devastation in St. Paul, Indiana. Several officials -- including Jeffersonville, Indiana, Mayor Mike Moore, U.S. Sen. Dan Coats and Adams -- indicated that the town of Marysville suffered especially significant damage.

Cavanaugh also said that the local high school, Henryville Junior-Senior High School, had been "demolished."

According to Sara Reschar, an administrative assistant for the West Clark Community Schools, "students were already out of the school when the storm hit" -- having been dismissed about 15 minutes earlier. Adams said there were some "scrapes and scratches," but no serious injuries as a result.

Authorities used thermal imaging equipment, search dogs and other means Friday night to look for a 9-year-old boy in Henryville whose whereabouts was unknown after the tornadoes came through, Adams said.

Amid the devastation, there was also some hope -- in the form of a 20-month-old girl found alone, and without identification, in a field in Salem, about 20 miles from Henryville.

Adam said the girl was intubated and then flown to Kosair Children's Hospital in Louisville. He said that people since had called in to identify the girl, while adding he did not know her current condition.

About four hours after the National Weather Service said a twister touched down in Indiana's Posey County, Gov. Mitch Daniels said crews "are racing the nightfall" to assess the damage and help those in need. Sgt. First Class Tina Eichenour of the Indiana National Guard said that roughly 250 troops have been called to duty, destined for towns such as Henryville and Marysville.

"I am constantly amazed by both the unpredictability and the ferocity that Mother Nature can unleash, when she chooses to," Daniels said of the severe weather.

His counterpart in Kentucky, Gov. Steve Beshear, on Friday declared a statewide emergency to facilitate local authorities' access to state resources. The governor has authorized the deployment of 50 National Guard troops to go to Morgan County to join a 12-person search and rescue team out of Lexington.

"The storm system hasn't cleared Kentucky yet, but we obviously have reports of some heavy damage," Beshear told CNN's Erin Burnett.

At least 12 people were killed in Kentucky tied to Friday's severe weather, authorities said.

Shawn Harley, from the National Weather Service, confirmed that people were trapped in damaged buildings after a large tornado struck the small town of West Liberty in eastern Kentucky.

There was no immediate word on casualties as a result. Chuck Wolfe, a spokesman for the Kentucky Emergency Management Agency, said state authorities had lost contact with the town.

Wolfe said officials believe the town "got hit pretty heavily." Beshear is expected to visit West Liberty to assess the damage Saturday.

Separately, a man in his 50s was found dead in his mobile home in Bethel, Ohio, the Clermont County Commissioners said in a press release.

In Tennessee, severe weather was responsible for critical injuries of as many as eight people in the cities of Harrison and Oolteweh, officials there said.

The storm brought golf-ball-size hail, strong winds and rain into the two northeast Alabama counties before continuing on a northeastward path into Tennessee.