Rescue crews worked into the rain-soaked chill of night, ignoring lightning and strong winds to dig through splintered homes, crumpled businesses and crushed cars in this Missouri town walloped by the deadliest single tornado in nearly six decades. Even more ominous: More storms, possibly strong ones, were on the horizon.

The death toll in Joplin reached 116 on Monday and was expected to climb. But there were glimmers of hope: Rescuers pulled 17 people from the rubble, and Gov. Jay Nixon vowed that crews would keep searching until everyone is accounted for.

"They still think there are folks that could be alive," Nixon told The Associated Press. Searchlights were brought in for work to continue overnight.

The killer tornado ripped through the heart of Joplin, a blue-collar southwest Missouri town of 50,000 people, Sunday night, slamming straight into St. John's Regional Medical Center. The hospital confirmed that five of the dead were patients _ all of them in critical condition before the tornado hit. A hospital visitor also was killed.

The tornado destroyed possibly "thousands" of homes, Fire Chief Mitch Randles told AP. It leveled hundreds of businesses, including massive ones such as the Home Depot construction store and Wal-Mart.

It was the second major tornado disaster in less than a month. In April, a pack of twisters roared across six Southern states, killing more than 300 people, more than two-thirds of them in Alabama.

In Joplin, much of the town's landscape was changed beyond recognition. House after house was reduced to slabs, cars were crushed like soda cans and shaken residents roamed streets in search of missing family members.

The danger was by no means over. Fires from gas leaks burned across town. The smell of ammonia and propane filled the air in some damaged areas. And the forecast looked grim.

The April tornadoes that devastated the South unspooled over a three-day period starting in the Plains. The Storm Prediction Center in Norman, Oklahoma, said a repeat could be setting up, with a possible large tornado outbreak in the Midwest on Tuesday and bad weather potentially reaching the East Coast by Friday.

"This is a very serious situation brewing," center director Russell Schneider said, citing a moderate risk of severe weather Tuesday in southwestern Missouri and in Oklahoma, Kansas and parts of North Texas.

Heavy rain fell from dark skies all day Monday, finally letting up only as night fell, and lightning was so frequent that it slowed the rescue and recovery effort, Randles said. A police officer from Riverside, Missouri, who was helping with the rescues, was burned from a lightning strike and hospitalized. Another officer was slightly injured in a near-lightning strike but kept working.

The twister that hit Joplin was one of more than 50 reported across seven Midwestern states over the weekend. One person was killed in Minneapolis and another in Kansas, but Missouri took the hardest hits.

At the destroyed Wal-Mart, perhaps 200 ruined cars lay crumpled in the parking lot. They were among thousands of shattered vehicles around town, including dozens of tractor-trailers tossed on their sides or tops.

Kim Weathers, 48, looked at her black Envoy and could only shake her head _ a piece of the roof from the Wal-Mart had pierced the windows and crushed the side of the SUV.

"We were in the store and all of a sudden somebody yelled, `Get down!' Weathers said. "I could feel the wind coming, then stuff was flying, hitting me in the head. I looked up and it was outside _ the roof was gone."

St. John's took a direct hit, leaving debris dangling from the top of the structure and blowing out almost every window. The town's other hospital, Freeman, was overflowing with patients, and makeshift hospitals and triage areas were set up at several other locations. More than 400 people were treated for injuries, Randles said.

Unlike the multiple storms that killed more than 300 people last month across the South, Joplin was smashed by just one exceptionally powerful tornado. Not since a June 1953 tornado in Flint, Michigan, had a single twister been so deadly. That storm also killed 116, according to the National Weather Service.

Nixon did not want to guess how high the death toll in Joplin would eventually climb. But he told AP: "Clearly, it's on its way up."

While many residents had up to 17 minutes of warning, rain and hail may have drowned out warning sirens. Some residents said the sirens are so common in "Tornado Alley" that they pay them little heed.

National Weather Service Director Jack Hayes said the tornado was given a preliminary label as an EF4 _ the second-highest rating assigned to twisters based on the damage they cause.

Once the center of a thriving mining industry, Joplin flourished though 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 Santa Monica, California, before freeways diminished the city's importance.

The community, named for the founder of the area's first Methodist congregation, is now a transportation crossroads and manufacturing hub. It's also the hometown of poet Langston Hughes and "Gunsmoke" actor Dennis Weaver.

City Manager Mark Rohr said the city "will recover and come back stronger than we are today."

Buck Nordyke, 53, planned to stay in his south Joplin home to ride out the rest of the storms, even though he's without power and has some slight roof damage.

"We could go to a neighbor's house or a hotel," Nordyke said. "But what about the next day, or what about the next day?"

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Associated Press writers David A. Lieb in Jefferson City, Kristi Eaton in Norman, Oklahoma, and Nomaan Merchant in Joplin contributed to this report.