The storm passed right through the heart of the city, wreaking havoc on landmarks large and small. It blew the windows out of Ted Turner’s restaurant, called Ted’s Montana Grill, and the Tabernacle, a popular concert venue. Skyscrapers were pocked with broken windows and billboards were twisted into skeletal scaffolds. Debris and glass carpeted the usually busy streets, making them impassible.

Brenton Young, a dentist from Shelby, N.C., had just put his drink order in at Thrive, a chic downtown restaurant, when street-level windows started exploding. “People were jumping up and screaming,” Mr. Young said. “We didn’t know if a car had hit the building or what had happened. People were hitting the floor. People were running for the center. It was a chaotic three seconds.”

Cheryl Denton, also in town for the convention, said she was in her hotel when the storm hit. “It just came up all of a sudden,” she said. “We looked out the window and stuff started swirling, and it was there and gone that quick.”

Her friend Dwayne Hawkins added, “It was on the news and it hit 15 minutes later.”

At a 2 a.m. news conference Saturday, Kelvin J. Cochran, the fire and rescue chief, said it would take 24 to 36 hours to complete the search and rescue operation.

Image Water pours down the steps at the Georgia World Congress Center in Atlanta. Credit... Phil Coale/Associated Press

One of the 11 people who were taken to Grady Hospital had life-threatening injuries, a spokeswoman for the hospital said, but by Saturday morning the condition of that victim had been upgraded to stable. The 10 others had been treated and released.

A few blocks away, where the Southeastern Conference men’s basketball playoffs were under way, players from both teams froze, mouths gaping on the court, when part of the fabric roof was torn away by the force of the storm, allowing a sudden gush of wind to blow through the Georgia Dome. Catwalks at the top of the dome swayed and bits of insulation rained down on players and fans during overtime of the Mississippi State-Alabama game, halting play and sending spectators scrambling for the exits.