The state medical examiner's office cut the estimated death toll by more than half but warned that the number was likely to climb again. Gov. Mary Fallin said authorities did not know how many people were still missing, but vowed to account for every resident.
"We will rebuild, and we will regain our strength," said Fallin, who went on a flyover of the area and described it as "hard to look at."
Amy Elliott, a spokeswoman for the medical examiner, said she believes some victims were counted twice in the early chaos of the storm that struck Monday afternoon. Downed communication lines and problems sharing information with officers exacerbated the problem, she said.
"It was a very eventful night," Elliott said. "I truly expect that they'll find more today."
Authorities initially said as many as 51 people were dead, including 20 children.
New search-and-rescue teams moved at dawn Tuesday, taking over from the 200 or so emergency responders who had worked all night. A helicopter shined a spotlight from above to aid in the search.
Many houses have "just been taken away. They're just sticks and bricks," the governor said, describing the 17-mile path of destruction.
The National Weather Service said the twister was on the ground for 40 minutes, with winds estimated at 190 mph. The agency issued an initial finding that the tornado was EF-4 on the enhanced Fujita scale - the second strongest type of tornado - and that it was at least half a mile wide.
Emergency crews were having trouble navigating neighborhoods because the devastation is so complete, and there are no street signs left standing, Fallin added.
Fire Chief Gary Bird said fresh teams would search the whole community at least two more times to ensure that no survivors - or any of the dead - were overlooked. Crews painted an 'X' on each structure to note it had been checked.
"That is to confirm we have done our due diligence for this city, for our citizens," Bird said.
The community of 56,000 people, 10 miles south of Oklahoma City, braced for another long, harrowing day.
"As long as we are here ... we are going to hold out hope that we will find survivors," said Trooper Betsy Randolph, a spokeswoman for the Oklahoma Highway Patrol.
More than 200 people had been treated at area hospitals.
Other search-and-rescue teams focused their efforts at Plaza Towers Elementary, where the storm ripped off the roof, knocked down walls and turned the playground into a mass of twisted plastic and metal as students and teachers huddled in hallways and bathrooms.
Fallin said she arrived in Moore late Monday and observed the search and rescue operation at the school.
"It was very surreal coming upon the school because there was no school," she said at the Tuesday news conference.
Earlier, she described her astonishment at the destruction, saying: "It would be remarkable for anyone to survive."
Seven of the nine dead children were killed at the school, but several students were pulled alive from under a collapsed wall and other heaps of mangled debris. Rescue workers passed the survivors down a human chain of parents and neighborhood volunteers. Parents carried children in their arms to a triage center in the parking lot. Some students looked dazed, others terrified.
Officials were still trying to account for a handful of children not found at the school who may have gone home early with their parents, Bird said Tuesday.
Many parents of missing schoolchildren initially came to St. Andrews United Methodist Church, which had been set up as a meeting site. But only high school students were brought to the church, causing confusion and frustration among parents of students enrolled at Plaza Towers. They were redirected to a Baptist church several miles away.
"It was very emotional - some people just holding on to each other, crying because they couldn't find a child; some people being angry and expressing it verbally" by shouting at one another, said D.A. Bennett, senior pastor at St. Andrews.
After hearing that the tornado was headed toward another school called Briarwood Elementary, David Wheeler left work and drove 100 mph through blinding rain and gusting wind to find his 8-year-old son, Gabriel. When he got to the school site, "it was like the earth was wiped clean, like the grass was just sheared off," Wheeler said.
Eventually, he found Gabriel, sitting with the teacher who had protected him. His back was cut and bruised and gravel was embedded in his head - but he was alive. As the tornado approached, students at Briarwood were initially sent to the halls, but a third-grade teacher - whom Wheeler identified as Julie Simon - thought it didn't look safe and so ushered the children into a closet, he said.
The teacher shielded Gabriel with her arms and held him down as the tornado collapsed the roof and starting lifting students upward with a pull so strong that it sucked the glasses off their faces, Wheeler said.
"She saved their lives by putting them in a closet and holding their heads down," Wheeler said.
The tornado also grazed a theater, and leveled countless homes. Authorities were still trying to determine the full scope of the damage.
Roofs were torn off houses, exposing metal rods left twisted like pretzels. Cars sat in heaps, crumpled and sprayed with caked-on mud. Insulation and siding was smashed up against the sides of any walls that remained standing. Yards were littered with pieces of wood, nails and pieces of electric poles.
President Barack Obama declared a major disaster and ordered federal aid to supplement state and local recovery efforts.
"Among the victims were young children trying to take shelter in the safest place they knew - their school," he said Tuesday.
The town of Moore "needs to get everything it needs right away," he added.
Obama spoke following a meeting with his disaster-response team, including Homeland Security Secretary Janet Napolitano and top White House officials.
The Storm Prediction Center in Norman, Okla., forecast more stormy weather Tuesday in parts of Texas, Arkansas, Louisiana and Oklahoma, including the Moore area.
In video of the storm, the dark funnel cloud can be seen marching slowly across the green landscape. As it churns through the community, the twister scatters shards of wood, awnings and glass all over the streets.
Monday's tornado loosely followed the path of a killer twister that slammed the region with 300 mph winds in May 1999. It was the fourth tornado to hit Moore since 1998.
The 1999 storm damaged 600 homes and about 100 businesses. Two or three schools were also hit, but "the kids were out of school, so there were no concerns," recalled City Manager Steve Eddy.
At the time of Monday's storm, the City Council was meeting. Local leaders watched the twister approaching on television before taking shelter in the bathroom.
"We blew our sirens probably five or six times," Eddy said. "We knew it was going to be significant, and there were a lot of curse words flying."
Betty Snider, 81, scrambled inside with her son and husband. She put her husband, who recently had a stroke, in a bathroom, but there wasn't room for both of them. So she and her son huddled in a hallway.
"That is the loudest roar I've ever heard in my life," she said.
She said she didn't have time to do anything. She couldn't duck, couldn't cover her ears, couldn't find another place to hide.
She said this was the closest a twister had ever come to her house, which remained standing.
Monday's twister also came almost exactly two years after an enormous tornado ripped through the city of Joplin, Mo., killing 158 people and injuring hundreds more.
That May 22, 2011, tornado was the deadliest in the United States since modern tornado record keeping began in 1950, according to the National Oceanic and Atmospheric Administration. Before Joplin, the deadliest modern tornado was June 1953 in Flint, Mich., when 116 people died.
Associated Press writers Tim Talley and Ramit Plushnik Masti; and Associated Press photographer Sue Ogrocki contributed to this report.