Rescuers scaled heaps of rubble to listen for survivors trapped in debris left by a tornado that ripped through communities in Indiana and Kentucky, killing 22 people. The tornado, the deadliest to hit Indiana since 1974, struck a horse-racing track near Henderson, Kentucky, then crossed into Indiana, triggering emergency sirens that many people fast asleep early Sunday did not hear. At least 17 people, including three children, died at a mobile home park in Vanderburgh County and five others died in neighboring Warrick County, east of Evansville. More than 100 people were taken to hospitals. "They were in trailer homes, homes that were just torn apart by the storm," Deputy Vanderburgh County Coroner Annie Groves said. "It's just terrible." As darkness fell Sunday night, rescuers set up lights to continue searching Eastbrook Mobile Home Park. They roamed what had been yards or basements, holding flashlights and lifting debris to make sure no one was underneath. They searched for several hours after dark before breaking off for the night. Cranes lifted toppled mobile homes, and forklifts moved smashed cars into organized rows. Other heavy equipment rumbled through the debris as night fell and the air became crisp and cool. All the dead were in Indiana. The youngest victim was a 2-year-old boy who was killed along with his 61-year-old grandmother, the coroner's office said. Although the possibility of finding survivors seemed to diminish as the day wore on, there were glimmers of hope. Firefighters were elated to find a child trapped, but alive, beneath part of a mobile home. "That's what it's all about," said Perry Township fire Chief Jerry Bulger, holding back tears as he spoke of the child's rescue. Indiana officials said the sirens sounded twice, but many in the mobile home park said they did not hear them. Emergency officials say the tornado warning sirens are loud enough to warn people who are outside but might not reach those tucked in bed. "They're not really designed to wake people up in the middle of the night," said John Buckman, fire chief of German Township Fire Department in Vanderburgh County. National Guard troops were called in to help with search-and-recovery efforts. Gov. Mitch Daniels toured Vanderburgh and Warrick counties Sunday to survey the damage. Indiana homeland security spokeswoman Pam Bright said the tornado was the deadliest in Indiana since April 3, 1974, when tornadoes killed 47 people. Those storms were part of one of the worst tornado outbreaks in U.S. history, which killed more than 300 in the South and Midwest and devastated Xenia, Ohio. In western Kentucky, the tornado ripped through Ellis Park racetrack, killing three horses and destroying large sections of the grandstand. Northern Crittenden county and the Hart County town of Munfordville also reported damage. Ryan Presley, a meteorologist with the National Weather Service, said the tornado appears to have been an F3 on the Fujita scale, with winds ranging from 158 mph (254 kph) to 206 mph (331 kph). The scale ranges from F0, the weakest, to F5.