* Death toll rises to 18
* More than 100 injured (Updates with comments from Arkansas governor)
By Steve Barnes
LITTLE ROCK, Ark., April 28 (Reuters) - Workers searched for survivors on Monday in the rubble left by a wave of tornadoes that ripped through the south-central United States a day earlier, killing at least 18 people in Arkansas, Oklahoma and Iowa.
Arkansas was the hardest hit, with at least 16 people dead. Neighborhoods were torn apart in central Faulkner County, where at least 10 people died in the storm system that produced that first fatalities of this year's U.S. tornado season, authorities said.
"It was a devastating tornado," Arkansas Governor Mike Beebe told a news conference, saying the main focus was on finding and rescuing victims.
The White House said President Barack Obama, who has been on a trip abroad, called Beebe to receive an update on the damage and to offer his condolences.
Strong winds wrenched houses off their foundations and flipped cars on top of the rubble in the small town of Vilonia in Faulkner County. Nine of the victims in the county lived on the same street in Vilonia, where at least 60 homes were destroyed, local broadcaster KARK TV reported.
Medical officials reported at least 100 people in Arkansas were injured.
"It's so heartbreaking. I've never seen destruction like this before," U.S. Representative Tim Griffin told reporters after touring Vilonia. "I saw a Dr. Seuss book in the rubble. I saw a Spider-Man shirt in the rubble. It just breaks your heart."
At dawn, heavy equipment was used in Vilonia and nearby Mayflower to clear debris off the streets or to load rubble onto trucks for removal.
"We could feel the house lifting up and swirling around. We were praying. The Lord kept us all safe," Sean Sellman, a resident of Vilonia, told KTHV-TV.
A tornado that hit the east side of Mayflower Sunday evening killed at least one person, tore up trees and brought down power lines, making it difficult for emergency personnel to find stricken areas in the dark, officials said.
More than 10,000 people were without power in Arkansas on Monday, officials said.
The Arkansas National Guard was deployed to help. Beebe declared a state of disaster for Faulkner and two other counties.
One person was killed in neighboring Oklahoma and another in Iowa, state authorities said.
A tornado in Baxter Springs, Kansas that touched down on Sunday evening destroyed as many as 70 homes and 25 businesses and injured 34 people, of whom nine were hospitalized, state and county officials said. One person was killed in Kansas, likely due to the same storm system, officials said.
Weather officials said more storms were on their way to the areas hit by the tornadoes. (Additional reporting by Suzi Parker in Little Rock, Brendan O'Brien in Milwaukee, Carey Gillam and Kevin Murphy in Kansas City, Missouri, Lisa Bose McDermott in Texarkana, Ark., Kevin Murphy in Kansas City, Mo. and Curtis Skinner in New York; Writing by Jon Herskovitz; Editing by Scott Malone and Bernadette Baum)