* Oklahoma, Kansas, Nebraska and Iowa are hit by twisters
* More storms forecast for Sunday in Plains
By Steve Olafson
OKLAHOMA CITY, April 15 (Reuters) - Clean-up efforts were underway across the Midwest on Sunday after dozens of tornadoes ripped across the region, killing five people in one Oklahoma town, three of them young girls, after storm sirens failed to sound and houses were reduced to rubble.
Storms skipped through what is often called "Tornado Alley" in the U.S. Central and Southern Plains on Saturday and into Sunday, but the high winds and dozens of tornadoes mostly struck rural areas, sparing the region from worse damage.
The storms left thousands without power in Kansas, hit an aircraft fuselage production facility, and damaged up to 90 percent of homes and buildings in a small Iowa town. The governors of Kansas and Oklahoma declared states of emergency.
The stormy weekend wasn't over for the Midwest. The National Weather Service declared tornado watches in Arkansas through Missouri and into a corner of Illinois, as well as in parts of Iowa, Minnesota and Wisconsin. But the likelihood of the most destructive tornadoes was low.
Damaging thunderstorms were also predicted from Minnesota south to Texas into Sunday night, according to AccuWeather.com.
A twister struck the northwest Oklahoma city of Woodward after midnight on Sunday, catching many in the town of 12,000 people unaware when storm sirens failed to sound after lightning apparently disabled the warning system, Mayor Roscoe Hill said.
"This thing took us by surprise," Hill said. "It's kind of overwhelming."
The Woodward tornado killed three young girls and two adults, according to Amy Elliott of the Oklahoma Medical Examiner's Office. Two girls, ages 5 and 7, died along with a man thought to be their father in a mobile home park.
A 10-year-old girl and a man were also killed in the small community of Tangiers, just outside the Woodward city limits.
A total of 29 people were treated at Woodward Regional Hospital, chief executive officer Dave Wallace said. Of those, five were in critical condition and moved to other hospitals.
Woodward city manager Alan Riffel told CNN that all the missing people had been accounted for, but 89 homes and 13 businesses had been destroyed.
"It's remarkable we didn't have more loss of life," Governor Mary Fallin told a news conference, saying many Woodward residents had either gone to sleep or dropped their guard after an earlier series of storms swept through the area.
She spoke to several whose homes were struck, including a man who said he was asleep on his sofa with his dog when the tornado hit, depositing them unhurt in the backyard.
A tornado that struck Woodward in April 1947 still ranks as the deadliest in Oklahoma history, with 116 people killed, according to the National Weather Service.
In tiny Thurman, Iowa, population 250, some 75 percent to 90 percent of the town's buildings and homes were damaged or destroyed by the storm, Fremont County Emergency Management Coordinator Mike Crecelius said. Only minor injuries were reported.
The U.S. tornado season started early this year, with twisters already blamed for 62 deaths in 2012 in the Midwest and South, raising concerns that this year would be a repeat of 2011, the deadliest tornado year in nearly a century.
Some 550 people died in tornadoes last year, including 316 killed in an April outbreak in five Southern states, and 161 people in Joplin, Missouri, the following month.
The National Storm Prediction Center had an unofficial count of 98 tornadoes in Nebraska, Iowa, Kansas and Oklahoma, starting Saturday morning and going until early Sunday.
No deaths or serious injuries were reported in Kansas, but about 11,000 people were reported without power, most of them around Wichita, Sharon Watson, a spokesperson for the state's National Guard and emergency services, said in a statement.
The storm damaged a hangar at McConnell Air Force Base in Wichita and destroyed several homes around the area, authorities said.
Storm chaser Brandon Redmond, a meteorologist with the Severe Weather Alert Team, said the twister passed over his vehicle and lifted it 2 feet (60 cm) off the ground in an industrial area south of Wichita, the state's second-largest metropolitan area after the Kansas City metro area.
"The tornado literally formed over our vehicle," he told Reuters. "I've never been that scared in my life. ... We had power flashes all around us and debris circulating all around the vehicle, sheet metal, parts of a roof, plywood."
Sedgwick County Commission Chairman Tim Norton said the tornado missed downtown Wichita and heavily populated neighborhoods and passed through areas to the south and east where there are manufacturing businesses and mobile home parks.
"With the storms we saw coming our way, it could have been much worse," Norton said. "We lucked out."
The damage included a Spirit Aerosystems production facility that manufactures fuselages for Boeing's 7-series airplanes. A Spirit spokesman said the facility was shut down on Sunday after a tornado damaged the roof and knocked out power, but the company hoped to have the plant running again soon.
"We do believe that the majority of the operational capabilities and facilities are intact," spokesman Ken Evans said.