A massive storm system has spawned tornados along a broad swathe of the US Midwest, with one city in Missouri hit with such force that dozens of cars were overturned and entire neighbourhoods razed to the ground, leaving only a forest of splintered tree trunks behind.
An unknown number were killed in Joplin, in south-west Missouri, yesterday, and officials struggling to communicate without power and mobile phone services were wary of putting a figure on a death toll they feared would rise after daybreak.
Asked about a report that 24 people had died, city spokeswoman Lynn Onstot said grimly that officials were "afraid it may be more... Our fear is that's a low number."
The Missouri National Guard planned to search for the injured throughout the night.
The same storm system that produced the Joplin tornado sparked tornados from Oklahoma to Wisconsin.
At least one person was killed in Minneapolis. But the devastation in Missouri appeared to be the worst of the day, eerily reminiscent of the tornados that killed more than 300 people across the US South last month.
"You see pictures of World War II, the devastation and all that with the bombing. That's really what it looked like," said Kerry Sachetta, the principal of a flattened Joplin High School.
"I couldn't even make out the side of the building. It was total devastation in my view. I just couldn't believe what I saw."
Ms Onstot said the tornado was on the ground for nearly 4 miles (6km). It hit a hospital packed with patients and a commercial area including a construction store, numerous smaller businesses and restaurants and a grocery store.
An untold number of homes were destroyed and reduced to rubble.
St John's Regional Medical Centre appeared to suffer a direct hit. The staff had just a few moments' notice to hustle patients into hallways before the storm struck the multistorey building, blowing out hundreds of windows and leaving the facility useless.
In the car park, a helicopter lay crushed on its side, its rotors torn apart and windows smashed. Nearby, a pile of cars lay crumpled into a single mass of twisted metal.
Triage centres and shelters were set up around the city of about 50,000 people about 160 miles (260km) south of Kansas City.
Emergency management officials rushed heavy equipment to Joplin to help lift debris and clear the way for search and recovery operations.
Missouri Governor Jay Nixon declared a state of emergency, and President Barack Obama sent condolences to families of those who died in storms in Joplin and across the Midwest.
Jeff Lehr, a reporter for the Joplin Globe, said he was upstairs in his home when the storm hit but was able to make his way to a basement closet.
"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," he 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."
In Minneapolis, Minnesota, city spokeswoman Sara Dietrich said one death was confirmed.
She had no other immediate details. Only two of the 29 people injured there were hurt critically.
Though the damage covered several blocks in Minneapolis, it appeared few houses were totally demolished. Much of the damage was to roofs, front porches that had been sheared away, or smaller items such as fences and basketball goals.