Missouri tornado death toll passes 100
Officials in the US state of Missouri say at least 116 people are now confirmed dead after a tornado hit the city of Joplin on Sunday, crushing cars and flattening homes.
But Joplin official Mark Rohr also said seven people had been rescued.
A thunderstorm carrying hail and high winds was hindering ongoing search and rescue efforts on Monday afternoon.
Mr Rohr said the tornado cut a path six miles (10km) long through the city, much of which is now without power.
Missouri governor Jay Nixon said he was "optimistic that there are still lives out there to be saved".
More than 1,150 people have been treated for injuries stemming from the tornado, the Joplin Globe newspaper reported.
The tornado knocked down power lines and telephone services remain largely cut off.
Joplin fire chief Mitch Randles said approximately one quarter or more of the city, home to about 50,000 people, had been damaged.
Roughly 2,000 buildings were damaged in the region, officials said.
Mr Nixon has declared a state of emergency and warned that more storms were on the way.
Cities in three other Midwestern states have also been badly affected. At least one person was killed in Minneapolis, Minnesota.
The White House said on Monday that President Barack Obama was being kept up-to-date on the deadly storms in the Midwest during his six-day trip in Europe.
Federal Emergency Management Agency administrator Craig Fugate is being sent to Missouri to help coordinate disaster response and recovery efforts, the White House added.
Last month, tornadoes and storms killed at least 350 people in Alabama and six other southern states.
Tornado sirens rang 20 minutes before the storm struck Joplin's city centre.
"There was a loud huffing noise, my windows started popping. I had to get downstairs, glass was flying. I opened a closet and pulled myself into it," Jeff Lehr, a reporter for the Joplin Globe newspaper, told the Associated Press.
"Then you could hear everything go. It tore the roof off my house, everybody's house. I came outside and there was nothing left."
Another resident, Tom Rogers, said his house had been destroyed.
"It's just gone," he told the Joplin Globe. "We heard the tornado sirens for the second time. All of a sudden, everything came crashing down on us. We pulled our heads up and there was nothing."
Much of the city's south side is reported to have been levelled, with churches, schools, businesses and homes reduced to rubble.
Nearly 100 patients at the St John Regional Medical Center were evacuated after the hospital took a direct hit.
A resident living 45 miles (70km) away said debris from the hospital had landed in his yard, including medical supplies and X-rays.
A door-to-door search of the damaged area began on Monday morning, but progress was slow because of the thunderstorm, and the danger from downed power lines and gas leaks, which caused fires around the city overnight.
Earlier, the Red Cross opened a shelter at Missouri Southern State University in Joplin for victims, spokeswoman Joanne Muir told the BBC.
Upon arriving in Ireland on Monday afternoon, President Obama phoned Governor Nixon to express his condolences for the devastation in Missouri.
Mr Obama had released a statement earlier in the day about the destruction, while en route to Europe.
"Michelle and I send our deepest condolences to the families of all those who lost their lives in the tornadoes and severe weather that struck Joplin, Missouri, as well as communities across the Midwest today," the president said.
Jay Nixon said storms had caused extensive damage across Missouri.
"As a state, we are deploying every agency and resource available to keep Missouri families safe, search for the missing, provide emergency medical care, and begin to recover," he said.
He warned that the storms were not finished and urged Missourians to keep a close eye on the latest weather information.