At least four people died as severe thunderstorms, powerful winds and apparent tornadoes ripped across swaths of the southeastern United States on Tuesday, downing power lines and trees, and damaging buildings.

The severe weather was part of a weather system wreaking havoc across much of the eastern third of the country.

Images circulating online from Panama City, Fla., showed homes whose roofs had been torn off, flattened buildings and impassable roadways after a reported tornado tore through the area early on Tuesday. In some areas north of the Alabama state line, storms brought hail the size of baseballs.

One person was killed and two others were critically injured after a strong storm moved through a mobile home park in Claremont, N.C., just after noon on Tuesday, according to officials in Catawba County.

In Houston County, Ala., an 81-year-old woman was killed when her mobile home was lifted off its foundation, the authorities said. And in Clayton County, Ga., south of Atlanta, one person was killed when a tree fell across a car’s windshield.

A man was also crushed to death by a falling tree in Birmingham, Ala., on Tuesday morning, the local station WVTM reported, citing the local fire and rescue department.

At one point on Tuesday afternoon, more than 22 million people were under tornado watches from Florida to Virginia. Later on Tuesday night, the number of people under tornado watches dropped to about 12 million as the threat of severe weather began to diminish in some states such as Georgia and South Carolina.

Still, the National Weather Service cautioned that strong tornadoes were possible in Florida, and that portions of North Carolina and Virginia could see storms with winds of up to 70 miles per hour.

There were at least 10 reports of tornadoes across the South by Tuesday afternoon, according to the Storm Prediction Center at the National Weather Service, though those remained unconfirmed until emergency officials and the Weather Service could survey the damage. The Weather Service said it would send crews to assess damage on Wednesday in Walton, Bay and Jackson counties in Florida. Crews were expected to look at damage on Thursday in Houston, Alabama and Calhoun counties in Georgia.

The Weather Service also planned to examine storm damage in Claremont, N.C., about 40 miles northwest of Charlotte, to see whether a tornado touched down in the area.

Gov. Ron DeSantis of Florida issued a state of emergency for 49 counties to “ensure that there are no unmet needs following the severe weather” affecting the state. He urged residents to heed the warnings of local officials.

The line of severe storms was expected to move across the Southeast on Tuesday, the Weather Service said, adding that it could cause more “widespread destructive wind gusts,” with speeds of 75 m.p.h. Power outages were affecting some areas, the Walton County Sheriff’s Office said on Tuesday.

By early afternoon, a tornado threat had moved through North Florida and into south-central Georgia, the National Weather Service in Tallahassee said.

“It’s going to take a while to clear the whole Southeast U.S.,” said Felecia Bowser, the head meteorologist for the Weather Service in Tallahassee.

In Bay County, Fla., the sheriff’s office urged residents to stay off the roads while emergency personnel rushed to damaged houses to investigate whether people were trapped. The authorities were working to survey storm-hit areas, including an apartment complex that the sheriff’s office said had “sustained extensive damage.” Power lines dangled low by some roadways, while others were obstructed with downed trees, debris and water, the office said.

Schools in Bay County, which includes Panama City, were closed on Tuesday, the school district said, adding that it was still surveying damage to structures.

In Georgia, emergency management officials had warned residents to prepare for storms, saying those in Southwest Georgia faced the highest risk of tornadoes, possibly beginning even before sunrise.

As of early Wednesday morning, more than 39,000 customers, mostly in central and southwestern counties, were without power, according to PowerOutage.us, which aggregates data from utilities across the United States.

In Georgia, schools in 27 of the state’s 159 counties were closed because of the severe weather, according to the Georgia Emergency Management and Homeland Security Agency. It said it was too early for an assessment of any damage.

Johnny Diaz and Mike Ives contributed reporting.