A swath of uprooted and broken trees, downed utility lines, peeled-off roofs and collapsed brick walls marked the path of the tornado that struck around 9:40 p.m. Friday.
"This was clearly a tornado," Lans Rothfusz of the National Weather Service's Peachtree City, Georgia, office said. He rated the storm an EF-2 on the Enhanced Fujita scale, meaning it packed top winds of 130 miles per hour.
Utility and cleanup crews worked Saturday to restore traffic lights, clear streets and remove tons of debris in the city's business district after Friday night's unusual urban storm.
Atlanta Mayor Shirley Franklin and Georgia Gov. Sonny Perdue declared states of emergency.
Police in Atlanta were urging people to stay away from downtown, fearing shattered glass and hanging metal would continue to fall from buildings as new storms rolled through.
A heavy thunderstorm prompted another tornado warning as it plowed across Atlanta just south of downtown Saturday afternoon. More storms were seen forming in Alabama and heading toward Atlanta.
At least two people were killed Saturday afternoon as the same line of storms destroyed structures elsewhere in northern Georgia.
Trees blown down in Friday night's storm crushed a row of houses in the city's historic Cabbagetown district just east of downtown.
Initial estimates from the mayor's office said at least 20 of the historic homes were damaged or destroyed by the tornado.
Atlanta police Maj. Renee Propes urged people to stay away from Cabbagetown.
About 10,000 customers were without power Saturday morning, according to Georgia Power, but by about 5:35 p.m. Saturday that number had mushroomed to 41,000 customers statewide. Crews were working to restore power but were pulled back when waves of bad weather threatened.
Earlier, Georgia Power spokesman John Sell said more than 40 power poles were broken by Friday night's tornado.
Some customers will not have power restored until Sunday, Sell said -- and it could be even longer if weather hinders crews' efforts.
Part of Atlanta's MARTA mass-transit rail system was shut down because of damage east of downtown.
The twister is the first to strike downtown Atlanta since record-keeping began in the late 1800s, said Laura Griffith, a National Weather Service forecaster.
On March 24, 1975, a tornado hit the city's Buckhead area, including the governor's mansion, she said. Three people died and more than 150 were injured.
The weather service said Friday's tornado plowed a path about 6 miles long and 200 yards wide.
The twister appears to have first struck several houses and churches in the Vine City neighborhood west of the business district, then moved on to the Georgia Dome, CNN Center, Centennial Olympic Park and Cabbagetown.
A brick apartment building in Vine City was roofless Saturday morning.
Curtains waved through broken windows high up the cylindrical 73-story Westin Peachtree Plaza hotel downtown. Gaping holes were torn in the roof of the Georgia World Congress Center, and an auto parts warehouse just east of downtown partially collapsed.