Fire Chief Gary Bird said he's "98 percent sure" there are no more survivors or bodies to recover under the rubble in Moore, a suburb of Oklahoma City with about 56,000 people.
The medical examiner's office on Tuesday lowered the death toll to 24 people, including nine children. Officials previously said 51 people were killed. The medical examiner believes some of the victims may have initially been counted twice in the early chaos.
At least 242 people have been treated at area hospitals. No additional survivors or bodies have been found since Monday night, Bird said.
Neighborhoods in Moore were leveled when they were hit with a twister that brought winds of more than 200 mph Monday. The National Weather Service said the tornado was an EF5 twister, the most powerful type. The agency upgraded the tornado from an EF4 based on what a damage-assessment team saw on the ground, spokeswoman Keli Pirtle said Tuesday.
During a Tuesday morning news conference, Oklahoma Gov. Mary Fallin said the town of Moore will rebuild.
"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."
The tornado's path was 17 miles long and 1.3 miles wide. Many houses have "just been taken away. They're just sticks and bricks," the governor said. Approximately 38,000 residents are without power.
Emergency crews were having trouble navigating neighborhoods because the devastation was so complete, and there are no street signs left standing, Fallin said.
Overnight, soldiers from the Oklahoma National Guard secured a perimeter around Plaza Tower Elementary School, which was one of two schools that took a direct hit.
"Among the victims were young children trying to take shelter in the safest place they knew, their school," President Barack Obama said.
Mr. Obama called the devastation "one of the most destructive tornados in history." The president offered prayers and said there's a long road of recovery ahead.
On Monday night, Mr. Obama approved a major disaster deceleration for Oklahoma, enabling federal funding and assistance to support immediate response and recovery efforts.
Moore was hard hit by a monster of a tornado in 1999. That storm had the highest winds ever recorded near the Earth's surface. Forty-two people died.
After three days of severe storms, weathercasters say more severe weather is likely to come, with 9.5 million people at risk of seeing tornadoes.
Oklahomans are using Facebook to reunite tornado victims with their missing belongings. Leslie Hagelberg found debris outside her home nearly 90 miles away. She logged onto Facebook and saw that many of her neighbors had reported finding items from Moore. Hagelberg decided to create a Facebook group to help facilitate the effort. Thousands have joined the group and posted photos of possible lost items.
Local Los Angeles volunteers, all veterans with Team Rubicon, are preparing to leave for Oklahoma. On its website, Team Rubicon describes itself as a disaster relief group that deploys during disasters.
There are several ways you can help the tornado victims in Oklahoma. Donate to the American Red Cross by visiting www.redcross.org or by calling (800) RED-CROSS. You can also text "Red Cross" to 90999 to donate $10.