Dave Martin/AP

George Thomas, 71, walks through the debris of the Rosedale Community where his brother-in-law lives in Tuscaloosa, Ala. Authorities are continuing the search for victims over a week after killer tornadoes swept across the state.

TUSCALOOSA, Ala. -- Where is Johnnie Brown's sister? Or the friend Billie Sue Hall talked to every day? A week after tornadoes ripped neighborhoods to shreds across the South, there still are no answers.

It's unclear how many people are missing across the seven states where 329 deaths have been reported. There are 25 unaccounted for in Tuscaloosa alone, the mayor says, but that number could be off because of the chaos.

Cadaver dog teams across the region are scouring the debris to uncover whatever tragedies may remain, and even bad news would be comforting to anguished families.

Tracy Sargent's dog team took just minutes to do what humans searching for hours could not: Locate the body of a University of Alabama student in a maze of twisted trees and debris. The young man's father was there when the body was found in Tuscaloosa this week.

"(The father) went over there and bent over and touched his son and started talking to him," Sargent said. "And he hugged him, started crying, and told him that he loved him and that he would miss him."

Brown doesn't know if that sort of moment awaits him. A picture of his sister, Latoya, smiling in an elegant orange dress, is posted on a wall of the Tuscaloosa shelter where he is staying. "Missing," it says.

"When I think about it, man, I just want to be by myself. I don't want nobody talking to me, nothing," the 20-year-old said, his voice barely audible.

Brown said his 21-year-old sister had been visiting friends at Rosedale Apartments the day the tornado hit. Police are looking for her, and rescue crews who searched the complex Wednesday did not find her, but he said his family is starting to fear the worst.

He still tries calling Latoya's cell phone, but gets agitated every time as it goes straight to voice mail.

Efforts to pin down the number of missing have been complicated by factors including multiple reports of the same missing person, or survivors.

Alabama officials are declining to say how many people could be missing statewide, and are now even keeping mum about the state's official death toll as it re-examines the tally. They reduced the figure from 250 to 236 on Monday after accounting for a gruesome fact of the storm: Some victims had been counted more than once because parts of their bodies were found in more than one place.

The work of finding answers for families of the missing falls largely on the search and rescue teams combing the ruins of entire communities that were ripped from their foundations and thrown across hollows and hills on April 27.

On Thursday, the National Weather Service upgraded one of the tornadoes that hit Mississippi to the most powerful category: an EF-5, with winds topping 200 mph. Another Mississippi tornado in last week's outbreak had already been classified as a EF-5. This is the first time on record that two EF-5 twisters hit Mississippi on the same day, and the first time it's happened to any U.S. state since a pair hit Kansas in 1990.

In Tuscaloosa, officials say at least 41 people were killed when an EF-4 tornado with winds up to 190 mph mowed down some of the city's most densely populated neighborhoods.

The twister was so powerful that searchers have had trouble even knowing where to look. The body of the college student found this week, for instance, was about 300 yards from his home, which the tornado reduced to a concrete slab.

Some of those waiting for word on missing friends and relatives may end up getting good news. Billie Sue Hall, now in a shelter, hopes her friend and neighbor Betty Cunningham is simply staying with a relative or safe in another shelter.

Hall said she and Cunningham talked daily, including the day the tornado hit, but she hasn't been able to reach her since.

"If you get out of the storm," Hall said Cunningham told her, "I'll call you back."