The tornado that tore through an Oklahoma City suburb killing 24 people and destroying as many as 13,000 homes may have caused $2bn in overall damage, officials said.
Oklahoma Insurance Department spokeswoman Calley Herth told the AP news agency that the early damage tally is based on visual assessments of the disaster zone that stretches more than 27 kilometres and that Monday's tornado was on the ground for 40 minutes.
The financial cost of the tornado in Moore could be greater than the $2 bn in damage from a 2011 tornado that killed 158 people in Joplin, Missouri, Herth said, adding that the Joplin tornado left a smaller trail of destruction.
For the first time Wednesday, authorities provided a clearer accounting of the destruction in Moore, a town of about 56,000 in a central US region known as Tornado Alley. Moore was also hit by a massive tornado in 1999.
|Search for survivors for Oklahoma tornado continues
Up to 13,000 homes were destroyed or damaged and 33,000 people were affected in some way by the storm, Mick Cornett, Oklahoma City mayor, said at a news conference.
He also put the monetary damage estimate at between $1.5bn to $2bn.
Emergency officials were unable to put a figure on the number of people left homeless, because many people have been taken in by relatives and only a few dozen have stayed overnight at Red Cross shelters.
Six adults remain unaccounted for since the tornado, said Oklahoma Department of Emergency Management Director Albert Ashwood. It is possible those people had just "walked off'' their properties or could still be found in the rubble, Ashwood said.
President Barack Obama will travel to Moore on Sunday to view the damage first-hand and meet with victims and emergency personnel. Secretary of Homeland Security Janet Napolitano visited the area on Wednesday, pledging the government's support.
The National Weather Service said the tornado was a top-of-the-scale EF5 twister with winds of at least 322 kph, the first EF5 tornado of 2013.
The Oklahoma medical examiner's office announced that it has positively identified 23 of the 24 people who died in the tornado.
Nine children were among the 24 killed, including seven who died at Plaza Towers Elementary School, which took a direct hit by the deadliest tornado to strike the US in two years.
Mayor Glen Lewis said Wednesday he would propose an ordinance in the next couple of days to modify building codes to require that every new home in the town would have a reinforced tornado shelter.
Underground safe rooms are typically built below garages and can cost around $4,000.
Al Jazeera's John Hendren, reporting from Moore Oklahoma, said even after the lethal 1999 tornado, commercial and home builders have opposed new requirements for shelters to be installed.
Emergency crews had trouble navigating devastated neighbourhoods because there were no street signs left. Some rescuers used smartphones or GPS devices to guide them through areas with no recognisable landmarks.
More than 1,000 people had already registered for assistance from the Federal Emergency Management Agency, or FEMA, which sent hundreds of workers to Oklahoma to help with the recovery.
Emergency workers pulled more than 100 survivors from the debris of homes, schools and hospital.
Plaza Towers Elementary was one of five schools in the path of the tornado.
Oklahoma State Police Sergeant Jeremy Lewis said that rescuers "literally were lifting walls up and kids were coming out".
"They pulled kids out from under cinder blocks without a scratch on them," Lewis said.
The National Weather Service (NWS) predicted a 10 percent chance of more tornadoes in parts of Texas, Oklahoma, Arkansas, Kansas, Missouri and Illinois.
It said parts of four other states - Wisconsin, Indiana, Michigan and Iowa - had a five percent risk of tornadoes.