New storms on Wednesday threatened a devastated Missouri town still looking for survivors from one of the strongest tornadoes on record after deadly twisters struck neighboring US states.
A series of tornadoes touched down in Oklahoma late Tuesday, killing four people in a rural county and injuring another 60 across the state, according to local officials, who said the tornadoes narrowly missed the state capital.
"This is a very dangerous time right now," Governor Mary Fallin told CNN on Tuesday, urging Oklahomans to immediately take shelter from "several... huge tornadoes on the ground."
The belt of severe weather stretched across Oklahoma, northern Texas and Kansas, where two people died when high winds hurled a tree into a van on a highway, according to the state's emergency management agency.
The fresh storms threatened Missouri, where rescue workers in the town of Joplin were still searching for survivors and shocked residents were digging their belongings out of the ruins of their homes.
A massive mile-wide funnel cloud, with winds of up to 200 miles (320 kilometers) an hour, tore through Joplin with devastating force late Sunday, leaving 123 people dead and hundreds more missing.
Joplin city manager Mark Rohr told reporters that rescue efforts were driven by an increasing sense of urgency, saying: "People's lives are at stake."
"We are still in search and rescue mode, and will be for the foreseeable future," he said after the disaster flattened much of this town of some 50,000 people.
Officials said the tornado ranks as the eighth deadliest in American history and the deadliest single twister to strike the United States since modern records began in 1950.
It has already exceeded the toll of a tornado in Flint, Michigan in 1953 that left 116 people dead.
More than 8,000 structures in this town bordering the heartland states of Kansas and Oklahoma were damaged or destroyed when the twister came roaring through with just a 24-minute warning.
It cut a swath of destruction four miles (6.4 kilometers) long and three quarters of a mile (more than a kilometer) wide.
Brandon Hicks, 26, was on an out-of-town fishing trip when the twister struck, but came home to discover that his house and his brother's house across the street were destroyed.
"We're trying to get everything salvaged, before the next storm hits," Hicks said as he sorted through the ruins.
Not far away, Lauren Miller, 23, wiped away tears as she sorted through family photos picked from the wreckage of her grandmother's home.
Miller's grandmother, who took shelter in the cellar with a neighbor as the house collapsed on top of them, survived.
But her other grandmother, who had been out for dinner Sunday evening to celebrate the high school graduation of a family friend, did not.
"It's not easy," Miller told AFP.
"I don't think the worst has come yet. This is all adrenaline and coping."
Some news reports said as many as 1,500 people were still unaccounted for, though there was hope that some might have found their way to homes of friends and relatives outside the immediate area.
On a hopeful note, 17 people were reported to have been pulled alive Monday from under the debris and rubble following the tornado, but only two emerged alive on Tuesday.
Officials vowed to keep up the "monumental task" despite an oncoming storm and the emotional and physical toll on the more than 600 rescuers.
"You're looking at something I don't think any human can imagine without seeing it -- it's just a devastating sight," said fire chief Mitch Randles.
"The fact that we are still retrieving live people is adding a great boost and just pushes our folks harder."
Desperate residents meanwhile phoned local radio stations seeking information about missing loved ones.
The town's Facebook page has become an online kiosk for news on which nearby restaurants are offering free meals and where to find emergency shelter.
US President Barack Obama plans to tour the disaster scene on Sunday.
"Our thoughts and prayers are with the families that are suffering at the moment," said Obama, who is on a four-nation European tour.
"All we can do is let them know that all of America cares deeply about them, and we are going to do absolutely everything we can to make sure they can recover."