KANSAS CITY, Missouri - A vicious ice storm sweeping through the U.S. Plains left more than 600,000 people without power as frigid temperatures plunged and contributed to at least 14 deaths, authorities said on Monday.

The icy blast downed tree limbs and power lines, leaving more than 500,000 people without power in Oklahoma, where shelters opened throughout the region for those driven from cold and dark homes, and national guardsmen and volunteers were transporting food and water to hard-hit areas.

"This particular storm is now the worst in company history in terms of customers affected," said Brian Alford, spokesman for Oklahoma Gas and Electric.

Crews were sent from Texas, Louisiana, Indiana and Mississippi to help repair power lines, which snapped seemingly as quickly as they could be repaired.

The storm also shut down electricity service to more than 102,000 people in Missouri, more than 11,000 people in Illinois and about 5,000 in Kansas.

In all, ice storm warnings were issued from Texas up through Oklahoma and Kansas and east across Missouri into Illinois, with up to an inch (2.5 cm) of ice accumulation possible in some areas. Iowa and Arkansas were also affected.

Missouri Gov. Matt Blunt declared a state of emergency, calling out the state National Guard to aid communities hit by the storm. "We are only just beginning to see the devastation from this series of storms," he said.

Ice-slicked roads contributed to the deaths of 12 people in Oklahoma during the weekend, state officials said. One Oklahoma man died of hypothermia. A Missouri motorist died when he stopped to help another driver and was hit by a car skidding on ice.

Parts of several highways and interstates were closed and hundreds of flights were cancelled at major airports in Chicago, Kansas City, St. Louis and Oklahoma City.

The National Weather Service office predicted another icy blast on Tuesday night, with more significant ice accumulations possible.