Survivors of the killer tornado that ripped through this Oklahoma City suburb rolled up their sleeves Wednesday under a blazing sun and got down to the long, hard task of rebuilding their lives.

Local authorities in Moore deemed it safe for everyone who lived within the 17-mile (27-kilometer) long disaster zone to return to their homes, or what little remained of their homes, to collect whatever belongings they could.

Twenty-four people died when the twister, packing winds of 200 miles per hour, cut through Moore with only a few minutes' notice Monday afternoon. Two of the fatalities were infants, just four and seven months old.

President Barack Obama is set to meet survivors Sunday and inspect the awesome scale of the destruction Sunday in a tight-knit community that suffered an even deadlier tornado in May 1999 that followed roughly the same track.

The preliminary causes of death for the two dozen fatalities included blunt force trauma, asphyxiation and, in the babies' case, head trauma, according to the Oklahoma Medical Examiner's Office.

Governor Mary Fallin's office updated the number of people injured to 353, from 237 earlier, and said that "all people thought missing have been accounted for at this time."

Touring the disaster zone, Homeland Security Secretary Janet Napolitano, who oversees the Federal Emergency Management Agency, pledged government support for those piecing their lives back together.

"At some point the cameras will leave, the national ones will leave first, then the local ones," she said. "But on behalf of President Obama and on behalf of FEMA, we will be here to stay until this recovery is complete."

Initial damage estimates are running as high as $2 million.

Moore Mayor Glenn Lewis said he would propose an ordinance to require storm shelters in all new homes. Few homes now have underground safe rooms, due to their high cost and the difficult nature of Oklahoma's flat clay terrain.

Fallin, speaking on CNN television, said it was "certainly wise" to install safe rooms, particularly in schools such as Park Towers Elementary, where seven children died.

While resembling a war zone, Moore buzzed with activity as utility crews reinstalled power lines, workers cleared scraps of debris from shopping center parking lots and rooftops, and insurance adjusters assessed damage claims.

"God Bless Moore," read the marquee of the Warren multiplex cinema, which suffered relatively little damage from the brunt of the storm that otherwise gutted shopping arcades and a nearby post office.

On residential side streets, homeowners returned with family and friends to pick through the rubble. Family photos were far and away the most sought-after items, along with clothing.

Binh Du, who works in Oklahoma City's booming IT industry, gestured under cloudless blue skies toward his neighbors' home during a break from salvaging items from his own destroyed three-bedroom home.

"I was lucky. At least I've got walls standing," said Du, 33.

Tiptoeing through the ruins with a friend, he recovered a stereo, a pair of bicycle tires and an erhu, a traditional Chinese string instrument. Even better, he found his two cats.

"This morning I found the first cat hiding in the living room," said Du, the Oklahoma-born son of Vietnamese refugee immigrants who was at work when the tornado touched down. "The second cat was in the closet."

Volunteers roamed the streets with free water and sports drinks. From Texas, a budget cellphone service turned up with a car trunk full of mobile phones to give away along with 200 minutes' worth of free calls.

Determined to resume normal life as soon as possible, Moore's three high schools announced they would go ahead with their graduation ceremonies as planned on Saturday.

On the Enhanced Fujita scale that measures a tornado's strength based on the damage it causes, the twister was an EF-5, the highest possible level, said Kelly Pirtle of the National Weather Service's Severe Storms Laboratory.

While the United States gets 75 percent of all the world's tornadoes, very few of them are greater than an EF-2, said John Snow, a meteorology professor and tornado expert at the University of Oklahoma.

The epic twister, cutting a swath two miles wide, flattened block after block of homes, hurling cars through the air, downing power lines and setting off localized fires in a 45-minute rampage.

The focal point of the tragedy was the Plaza Towers Elementary School, where frightened teachers and students huddled in hallways and bathrooms as the tornado barreled through, and where some of the children died.