Updated at 8:31 p.m. ET
JOPLIN, Mo. - Rescue crews dug through piles of splintered houses and crushed cars Monday in a search for victims of a half-mile-wide tornado that killed at least 116 people when it blasted much of this Missouri town off the map and slammed straight into its hospital.
Authorities were prepared to find more bodies in the rubble throughout this gritty, blue-collar town of 50,000 people about 160 miles south of Kansas City.
Gov. Jay Nixon told The Associated Press he did not want to guess how high the death toll would eventually climb. But he said: "Clearly, it's on its way up."
But there's good news too. Seventeen people were pulled alive from the rubble. An unknown number of people were hurt.
Authorities feared the toll could rise as the full scope of the destruction comes into view: House after house reduced to slabs, cars crushed like soda cans, shaken residents roaming streets in search of missing family members. And the danger was by no means over. Fires from gas leaks burned across town, and more violent weather loomed, including the threat of hail, high winds and even more tornadoes.
At daybreak, the city's south side emerged from darkness as a barren, smoky wasteland.
"I've never seen such devastation -- just block upon block upon block of homes just completely gone," said former state legislator Gary Burton who showed up to help at a volunteer center at Missouri Southern State University.
It was America's deadliest tornado since a June 1953 twister in Flint, Michigan, and authorities were prepared to find more bodies in the rubble throughout Joplin, a gritty, blue-collar town of 50,000 people about 160 miles south of Kansas City.
The storm was so powerful it reportedly ripped the bark from trees as wind speeds approached 150 miles per hour, CBS News correspondent Cynthia Bowers reports.
City Manager Mark Rohr said the twister cut a path nearly 6 miles long and more than a half-mile wide through the center of town. Much of the city's south side was leveled, with churches, schools, businesses and homes reduced to ruins.
"We're still in search-and-rescue mode," Rohr told CBS' "The Early Show." "We have a lot of structures that have been damaged and completely fallen to the ground, and we've got a lot of volunteers coming in, along with city forces and nearby forces that are going around into those damaged areas, seeking survivors and trying to affect a rescue for those people that are trapped."
Jasper County emergency management director Keith Stammer said about 2,000 buildings were damaged, while Joplin fire chief Mitch Randles estimated the damage covered a quarter or more of the city of about 50,000 people some 160 miles south of Kansas City. He said his home was among those destroyed.
An unknown number of people were injured, and officials said patients were scattered to any nearby hospitals that could take them.
As rescuers toiled in the debris, a strong thunderstorm lashed the crippled city. Rescue crews had to move gingerly around downed power lines and jagged chunks of debris as they hunted for victims and hoped for survivors. Fires, gas fumes and unstable buildings posed constant threats.
Teams of searchers fanned out in waves across several square miles. Many of the groups included specially trained dogs. The teams went door to door, making quick checks of property that in many places had been stripped to its foundations or had its walls collapse.
National Weather Service Director Jack Hayes said the storm was given a preliminary label as an EF4 -- the second-highest rating given to twisters. The rating is assigned to storms based on the damage they cause. Hayes said the storm had winds of up to 198 mph. At times, it was 1,200 meters wide.
A series of gas leaks caused fires around the city overnight, and Gov. Nixon said some were still burning early Monday. Nixon said he feared the death toll would rise but also expected survivors to be found in the rubble.
"I don't think we're done counting," Nixon told The Associated Press, adding, "I still believe that because of the size of the debris and the number of people involved that there are lives to be saved."
President Obama, in Ireland on a European tour, called Nixon shortly after 8 a.m. ET to personally extend his condolences and to assure the governor that the Federal Emergency Management Agency will remain in close contact and coordinate with state and local officials, CBS Radio News correspondent Peter Maer reports. Nixon has declared a state of emergency.
Mr. Obama directed FEMA Administrator Craig Fugate to travel to Missouri to ensure the state has all the support it needs, Maer reports.
(At left, President Obama talks on the phone with Missouri Gov. Jay Nixon during his visit to Dublin May 23, 2011.)
Crews found bodies in vehicles the storm had flipped over, torn apart and left crushed like empty cans. Triage centers and temporary shelters quickly filled to capacity. At Memorial Hall, a downtown entertainment venue, emergency workers treated critically injured patients.
At another makeshift unit at a Lowe's home improvement store, wooden planks served as beds. Outside, ambulances and fire trucks waited for calls. In the early hours of the morning, emergency vehicles were scrambling nearly every two minutes.
After daybreak, survivors picked through the rubble of their homes, salvaging clothes, furniture, family photos and financial records, the air pungent with the smell of gas and smoking embers. Some neighborhoods were completely flattened and the leaves stripped from trees, giving the landscape an apocalyptic aura. In others where structures still stood, families found their belongings jumbled as if someone had picked up their homes and shaken them.
Kelley Fritz, 45, of Joplin, rummaged through the remains of a storage building with her husband, Jimmy. They quickly realized they would never find the belongings they stored there, and they lost much of what was in their home after the tornado ripped away the roof. Their sons, ages 20 and 17, both Eagle Scouts, ventured outside after the storm.
"My sons had deceased children in their arms when they came back," Fritz said. "My husband and I went out and saw two or three dead bodies on the ground."
Twenty people at a convenience store darted into its cooler as the building began to collapse around them. A video camera inside recorded the group praying and crying as the storm hit in two separate waves. Brennan Stebbins, 23, said he thought he might die, but all were able to climb out of the rubble of the Fast Trip without major injuries.