JOPLIN, Missouri (AP) _ Rescue crews dug through piles of splintered houses and crushed cars Monday in a search for victims of a half-mile-(kilometer-)wide tornado that blasted much of this Midwestern town off the map and slammed straight into its hospital.

At least 116 people died, making it America's deadliest single tornado in nearly 60 years and the second major tornado disaster in a month. 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 (257 kilometers) south of Kansas City.

Despite the grim outlook, Gov. Jay Nixon said he was ``optimistic that there are still lives out there to be saved.''

While many residents had 10 to 17 minutes of warning, rain and hail may have drowned out the sirens.

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 (318 kph). At times, it was 1,200 meters wide.

Some of the most startling damage was at St. John's Regional Medical Center, where staff had only moments to hustle their patients into the hallway. Five patients died there, although it was not clear if they were patients or staff members.

The storm blew out hundreds of windows and caused damage so extensive that doctors had to abandon the hospital after the twister had passed. A crumpled helicopter lay on its side in the parking lot near a single twisted mass of metal that used to be cars.

Dazed survivors tried to salvage clothes, furniture, family photos and financial records from their flattened or badly damaged homes.

Last month, a ferocious pack of twisters roared across six Southern states, killing more than 300 people, more than two-thirds of them in Alabama.

As in the Midwest, the Southerners also had warning _ as much as 24 minutes. But those storms were too wide and too powerful to escape. They obliterated entire towns from Alabama to Virginia in what the weather service said was America's deadliest tornado outbreak since April 1974.

Forecasters said severe weather would probably persist all week. Arkansas, Kansas, Missouri and Oklahoma could see tornadoes through Tuesday, he said, and the bad weather could reach the East Coast by Friday.

The twister that hit Missouri was one of 68 reported across seven Midwest states over the weekend. One person was killed in Minneapolis and another in Kansas, but Missouri took the hardest hits.

Joplin, named for the founder of the area's first Methodist congregation, is the hometown of poet Langston Hughes. It flourished through World War II because of its rich lead and zinc mines. It also gained fame as a stop along Route 66, the storied highway stretching from Chicago to California before freeways diminished its importance.

Triage centers and shelters around Joplin rapidly filled to capacity. At a home-improvement store, wooden planks served as cots.

Kerry Sachetta, principal of a flattened Joplin High School, could barely recognize her own building.

“You see pictures of World War II, the devastation and all that with the bombing,'' she said. ``That's really what it looked like.''