Rescue workers searched for anyone still buried in the heaps of splintered wreckage left after a massive tornado obliterated most of Greensburg, Kansas.
At least 10 people were known dead from weekend storms -- eight in the Greensburg area and two others elsewhere in Kansas -- one on Friday night and another in violent weather late on Saturday, state officials said.
Amid the destruction, rescue workers and officials held out hope that the death toll wouldn't rise and that they can rebuild their town, from replacing the destroyed churches down to the town's fire engines.
"At this point, it's still a search and rescue mission," Kansas state trooper Ronald Knoefel said on Sunday. "We don't want to give up hope."
Search teams used trained dogs to sniff for bodies and used their hands and heavy equipment to clear away the rubble, but officials did not know how many people might still be missing.
"A lot of people have gone to other places and it's difficult to track them down," said Major General Tod Bunting, the state's adjutant general.
National Guard engineers were assigned to help with the search.
"Some of the rubble is just so deep," Bunting said. "That's really what our problem is."
The National Weather Service classified the Friday night tornado as an F-5, the highest category on its scale.
The weather service said it had wind estimated at 330kph, and carved a track 2.7km wide and 35km long.
The twister is the first classified as an F-5 since May 3, 1999, when a tornado killed 36 people in Oklahoma City on May 3, 1999.
This was the first F-5 since the weather service revised its scale this year, in an effort to more comprehensively gauge tornadoes' damage potential, with less emphasis on wind speed.
Tree trunks stood bare in Greensburg, stripped of most of their branches. All the churches were destroyed.
Every business on main street was demolished. The town's fire engines were crushed. The massive concrete silos of a grain elevator towered over the flattened expanse of what was left of the town.
Greensburg Administrator Steve Hewitt, who lost his home, estimated 95 percent of the town of 1,500 was destroyed.
Greensburg remained off limits to residents on Sunday, but officials said they would be allowed to return yesterday morning to recover what they could. Residents were to be bused in and would have to leave by 6pm.
On Sunday, the weather service posted tornado warnings during the afternoon for parts of Kansas and Oklahoma and severe thunderstorm warnings were extended across parts of Missouri, Kansas, Oklahoma and Texas.