JOPLIN, Mo. - Rescue crews dug through piles of splintered houses and crushed cars yesterday 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.

It was the nation's deadliest single tornado in nearly 60 years and the second major tornado disaster in less than a month.

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.

At daybreak, the city's south side emerged from darkness as a barren, smoky wasteland.

It was the nation's deadliest single twister since a June 1953 tornado in Flint, Mich. Unlike the multiple storms that killed more than 300 people last month across the South, Joplin was smashed by just one exceptionally powerful twister.

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. An unknown number of people were hurt.

Despite the grim outlook, Gov. Jay Nixon said he was "optimistic that there are still lives out there to be saved." He said 17 people had been rescued.

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. The groups went door to door, making quick checks of property that in many places had been stripped to their foundations or had walls collapse.

National Weather Service director Jack Hayes said the storm had winds of 190 to 198 mph. At times, it was three-quarters of a mile wide.

Some of the most startling damage was at St. John's Regional Medical Center. Six patients died there.

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

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

Kelley Fritz rummaged briefly through what was left of a storage building, then gave up. Her boys, both Eagle Scouts, rushed into the neighborhood after realizing every home was destroyed.

When they returned, she said, "my sons had deceased children in their arms."

The twister that hit Joplin was one of 68 reported across seven Midwest states over the weekend. One person was killed in Minneapolis and another in Kansas.