JOPLIN, Missouri (AP) — Rescue crews worked through the rain-soaked chill of night, ignoring lightning and strong winds to dig through splintered homes, crumpled businesses and crushed cars in this Missouri city 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 survivors 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.

Early Tuesday, Assistant City Manager Sam Anselm said no new victims or survivors had been found overnight.

The killer tornado ripped through the heart of Joplin, a working-class southwest Missouri city 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.

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. Hayes said the storm had winds of 190 to 198 mph (306 to 319 kph). At times, it was three-quarters of a mile (over a kilometer) wide.

The tornado destroyed possibly “thousands” of homes, Fire Chief Mitch Randles told AP. It leveled hundreds of businesses, including massive ones such as Home Depot and Walmart.

Speaking from London, President Barack Obama said he would travel to Missouri on Sunday to meet with people whose lives have been turned upside down by the twister. He vowed to make all federal resources available for efforts to recover and rebuild.

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“The American people are by your side,” Obama said. “We’re going to stay there until every home is repaired, until every neighborhood is rebuilt, until every business is back on its feet.”

Craig Fugate, director of the Federal Emergency Management Agency, told NBC’s “Today” show Tuesday that Obama has declared a disaster in the area, which means residents are eligible for his agency’s assistance.

“We’re here for the long haul, not just for the response,” Fugate said.

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 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 city. 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.

Early Tuesday, the center said there was a moderate risk of severe weather in central and southeast Kansas and southwestern Missouri, which could include Joplin. It raised the warning for severe weather in central Oklahoma, southern Kansas and north Texas to high risk indicating that tornadoes will hit in those areas.

The Storm Prediction Center also issued a high-risk warning before the deadly outbreak in the South in April.

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 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 rainy, cool weather — the forecast called for an overnight low of 62 degrees (17 Celsius) — raised concerns about its effect on anyone still trapped in rubble. A whipping wind, perhaps strong enough to finish off homes left barely standing by the tornado, made things more dangerous for searchers and potential survivors.

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 Walmart, perhaps 200 cars lay crumpled in the parking lot. They were among thousands of shattered vehicles throughout the city, including dozens of tractor-trailers tossed on their sides or tops.

Kim Weathers, 48, looked at her black GMC Envoy and could only shake her head — a piece of the roof from the Walmart 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 city’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.

Nancy Hood, 63, is bedridden after suffering from diabetes and cancer. She said she often ignores warning sirens, but didn’t on Sunday, telling her husband to grab their two grandsons, ages 4 and 7, and get to the hallway. The tornado destroyed most of Hood’s house — except the bedroom where she remained and the hallway.

“Praise God,” Hood said. “It was divine intervention.”

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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.

Copyright 2011 The Associated Press.