More than 50 deaths across nine states were blamed on the storm, the majority in car accidents on icy roads, US media reported. Several were killed by carbon monoxide poisoning from malfunctioning generators and heaters after the power went out.

A massive storm that began churning across the country on Friday brought ice, sleet, rain, flash floods and even a few tornadoes as it moved from the southwestern states of New Mexico and Texas to far northeastern Maine.

A winter storm warning was in effect Wednesday in parts of North and South Carolina, and a winter storm watch across New Mexico, Texas, Oklahoma and northeastern Maine, the National Weather Service said.

An icy snap in normally balmy California led Governor Arnold Schwarzenegger to warn that the region's citrus fruit industry could be devastated, with damage "close to a billion dollars."

California supplies nearly a quarter of citrus fruit sold in the United States, according to state agricultural authorities.

Snow forced the closure of a 60-kilometer (37-mile) stretch of one of California's biggest transport routes north of Los Angeles on Wednesday, transport authorities said.

Low temperatures also struck the US northwest, where cleanup crews in Portland, Oregon on Wednesday focused on de-icing major roadways after the area was hit with up to 13 centimeters (five inches) of snow on Tuesday.

Cars stuck in the snow were abandoned on Portland freeways, and transportation officials temporarily ordered all vehicles on the roads to use chains or snow tires.

City officials and forecasters predicted a light dusting and were unprepared for the heavy snowfall, local news media reported.

The sudden snowfall and slick roads also triggered a 30-car pileup on a major highway outside Seattle, Washington on Tuesday.

Low temperatures will keep the snow and ice on the ground in the northwest at least until Friday, according to local forecasts.

The storm that covered much of the midwestern US was caused by a vast cold front that dropped temperatures by as much as 17 degrees C (30 degrees F) and brought wave after wave of freezing rain and sleet as it moved slowly eastward.

It weakened somewhat by early Wednesday, sparing the major East Coast cities of New York, Boston and Philadelphia from the worst of the ice and sleet.

Schools and businesses remained closed in Oklahoma, Texas and Missouri where freezing rain and sleet knocked down trees and power lines and made driving conditions extremely dangerous.

President George W. Bush declared an emergency in Oklahoma on Sunday, and Federal Emergency Management Agency workers were in the state handing out emergency supplies.

The Oklahoma Highway Patrol reported more than 300 road accidents in which 14 people were killed and 128 people were hospitalized. Power companies said about 150,000 people statewide were still without electricity.

"Texas has still got all sorts of problems -- they have freezing rain, sleet and snow," said Dennis Feltgen, a spokesman for the National Weather Service. "In Oklahoma they have so many (power) lines down it's going to take a while to get things back up."

The weather service has also issued flood warnings for the Mississippi River Valley from Louisiana to Illinois and for Indiana and Ohio.

Bush also declared a state of emergency for Missouri -- including the city of St. Louis -- on Monday, freeing up federal funding for recovery efforts.

More than 300,000 people lost power in the state due to downed power lines, and a utility worker was injured, Missouri state officials said.

In the far northeastern state of Maine, temperatures early Wednesday were as low as minus 24 C (minus 11 F) but no major problems were reported.

Ski resorts welcomed the icy weather and fresh snow, which allowed them to open runs that have been closed during unseasonably mild temperatures over the Christmas and New Year holiday period.

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