The Associated Press. A destroyed apartment complex is seen in Joplin, Mo., on Tuesday. A large tornado moved through much of the city Sunday, killing at least 122 people and damaging a hospital and hundreds of homes and businesses.
JOPLIN, Mo. -- Emergency crews drilled through concrete at a ruined Home Depot, making peepholes in the rubble in hopes of finding lost shoppers and employees. A dog clambered through the shattered remains of a house, sniffing for any sign of the woman and infant who lived there.
Across devastated Joplin, searchers moved from one enormous debris pile to another Tuesday, racing to respond to any report of a possible survivor.
The human toll rose to at least 122 dead and 750 people hurt. But just nine had been pulled alive from the aftermath. Searchers fought the clock because anybody still alive after the deadliest single tornado in 60 years was losing precious strength two days after the disaster. And another round of storms was closing in.
For Milissa Burns, hope was fading that her 16-month-old grandson, whose parents were both hospitalized after the tornado hit their home, would be found.
She showed up Tuesday at a demolished dental office near the child's home to watch a search team. At one point, a dog identified possible human remains, prompting eight searchers to dig frantically, but they came away with nothing. Burns was weary but composed. Her daughter -- the boy's aunt -- sobbed next to her.
''We've already checked out the morgue,'' Burns said. ''I've called 911 a million times. I've done everything I can do. He was so light and little. He could be anywhere.''
Also Tuesday, the National Weather Service announced that the twister that crippled Joplin was an EF-5, the strongest rating assigned to tornadoes, with winds of more than 200 mph. Scientists said it appeared to be a rare ''multivortex'' tornado, with two or more small and intense centers of rotation orbiting the larger funnel.
It was the deadliest single twister since the weather service began keeping official records in 1950 and the eighth-deadliest in U.S. history.
Another top job was testing the city's tornado sirens to make sure they were operable ahead of another round of potentially violent weather starting Tuesday evening and expected to last into today in some places. Emergency officials warned jittery residents well in advance of the test.
David Imy, a meteorologist at the federal government's Storm Prediction Center in Norman, Okla., said conditions were ripe for severe thunderstorms, including tornadoes, in parts of Kansas, Missouri, Arkansas, Texas, Kentucky and Tennessee, as well as nearly all of Oklahoma.