At least seven Mississippi counties are trying to recover from a tornado that touched down Sunday, leaving widespread damage and at least 16 injured.
So far, no one has been reported killed, which authorities hope will remain true.
But at least two people were critically injured in Lamar County, the Mississippi Emergency Management Agency said.
The tornado struck Hattiesburg, the southern Mississippi city that straddles Lamar and Forrest counties.
Hattiesburg mayor Johnny DuPree reported major damage to structures around town. "If there is a good thing about this, it happened on a Sunday when most of these structures were vacant," he said.
The state emergency management agency said seven counties have reported damage. Several homes were destroyed in Marion County, and numerous homes, businesses and public buildings sustained "significant damage."
As of Monday morning, about 4,000 power customers are without electricity, Mississippi Power said. That's an improvement from the 13- to 14,000 customers who were without electricity at one point, but it's unclear when power would be restored to everyone, spokesman Mark Davis said.
Mississippi Gov. Phil Bryant declared a state of emergency for counties affected. The declaration allows for the use of state resources and assets to support local response efforts, MEMA said.
Hattiesburg is home to the University of Southern Mississippi. It suffered damage to several buildings, but there were no reports of injuries there.
University police declared a state of emergency and urged those not on campus to stay away until further notice.
Nearby Oak Grove High School also suffered damage. Randy Wright posted photographs to his Twitter account of the school, showing debris strewn on what looked to be a parking lot and a truck upside down in a baseball diamond.
The Hattiesburg Public School District canceled classes Monday. The university campus will also be closed.
"There's quite a few homes without power at this point. Quite a few trees on houses, on cars, that type of thing," said Forrest County Sheriff Billy McGee.
He said between 10 to 15 people were hospitalized, but that none suffered serious injuries.
It was not clear how those people were hurt.
Sarah Lawrence, a Hattiesburg resident, said that the storm sounded like "stuff being thrown."
"Within seconds, everything changed," she said. "I didn't feel like there was much notice. I heard the sirens and everything looked OK outside, so I started making preparations to go into the bathroom. And then, next thing I know, all the lights went out, and it got dark outside."
CNN's Maggie Schneider, Chandler Friedman, Elwyn Lopez and Janet DiGiacomo contributed to this report.
Associated Press story:
HATTIESBURG, Miss. (AP) -- Residents shaken by a tornado that mangled homes in Mississippi were waking up Monday to a day of removing trees, patching roofs and giving thanks for their survival. More than a dozen in the state were injured.
Daylight also offered emergency management officials the chance to get a better handle on the damage that stretched across several counties. Gov. Phil Bryant planned to visit hard-hit Hattiesburg, where a twister moved along one of the city's main streets and damaged buildings at the governor's alma mater, the University of Southern Mississippi. Emergency officials said late Sunday that at least 10 people were injured in surrounding Forrest County and three were hurt to the west in Marion County, but they weren't aware of any deaths.
Among those who felt lucky to be alive was 49-year-old Margie Murchison, who was visiting with a friend when her husband started screaming for them to take shelter from the approaching storm in a nearby culvert. They sprinted out of the house as debris flew around them and made it to the conduit that runs under the road. A tree crashed behind them as they made it to their hiding place.
"For a minute there, that wind was so strong I couldn't breathe," Murchison said.
Said Murchison's friend, 55-year-old Wayne Cassell: "If we had wasted any seconds, we wouldn't have made it."
After the storm passed, there were trees down all around the Murchison home. She said there was part of the roof damaged and leaking. Windows were broken out and the detached garage was leaning.
Mississippi Emergency Management Agency spokesman Greg Flynn said it appears a single tornado caused the damage in Forrest, Marion and Lamar counties. Hundreds of homes are damaged in Forrest County, along with a couple dozen in the other two.
Flynn said the sheer scope of the damage was slowing officials' assessment.
"The problem is, it was so strong that there's so much debris that there's a lot of areas they haven't been able to get to yet," he said.
On campus, trees were snapped in half around the heavily damaged Alumni House where part of the roof was ripped away. Windows in a nearby building
The university released a statement saying no one was hurt but that it was under a state of emergency, and anyone away from campus should stay away until further notice.
East of campus, 47-year-old Cindy Bullock was at home with her husband and dog, a terrier mix named Vinnie, when she heard the tornado coming. They ran to a hallway and covered their heads. It wasn't long before the windows in the kitchen and bedroom exploded. The storm stripped all the shingles off the roof and left holes in it, while knocking over a large pine tree in the yard.
After dark, the Bullocks were trying to arrange their stuff inside so it wouldn't get wet from the dripping water.
"I just looked out the window and I heard the rumbling. It sounded like a train. We ran to the hall, and the kitchen windows and the windows in the bedroom exploded. It happened pretty fast," she said.
There were large trees blocking the road all through her neighborhood, and several of the houses were hit by falling trees. Her friend was staying with them after the friend's apartment took a direct hit from a falling tree.
Forrest County Sheriff Billy McGee says 10 or 15 people were injured by the tornado that slammed Hattiesburg and other parts of the county - but none of the injuries was serious.
"Most of our injuries have been walking wounded," he said.
To the west, Marion County emergency director Aaron Greer said three injuries had been reported in the community of Pickwick, about seven miles south of Columbia. Two people were taken to hospitals, but the third didn't have the injury examined, he said.
Greer said one mobile home was destroyed, three other structures have major damage and several have minor damage.
On Sunday night, John and Katherine Adams were cleaning up around their one-story white house where the storm punched holes in the roof, busted windows and completely destroyed the back porch. The couple was at home with their 7- and 3-year-old daughters when the tornado passed next to their house.
All through the neighborhood, houses and vehicles were damaged by falling trees.
"We're safe, and that's all that matters," said Katherine Adams, 46.
John Adams, who's in the building supply business, said he was surprised to see broken boards that appeared to be from new construction in his yard because there are no homes being built nearby.
"We've got stuff around here; I don't even know where it came from," he said.
McConnaughey reported from New Orleans.