WASHINGTON, Dec. 10 (Xinhua) -- An ice storm sweeping through the U.S. Plains left more than 600,000 people without power and caused at least 14 deaths, local authorities said Monday.

    The storm downed branches and power lines, leaving more than 500,000 people without power in Oklahoma, where shelters were set up 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, the state's largest utility firm.

    The storm also shut down the electricity service to more than 102,000 people in Missouri, more than 11,000 people in Illinois and about 5,000 people in Kansas. Crews were sent from Texas, Louisiana, Indiana and Mississippi to help repair power lines.

    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.

    A state of emergency was declared Monday for all of Oklahoma, and Missouri declared an emergency Sunday and put the state National Guard on alert. Meanwhile, a state of emergency was declared for all of Kansas.

    Ice-covered roads caused the deaths of 12 people in Oklahoma during the weekend, according to state officials. Missouri had two storm-related deaths: one on a slippery highway and another when a tree branch fell on a 92-year-old man's head.

    Parts of several highways and interstates were shut down, 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 ice storm Tuesday night, with more significant ice accumulations possible.