Updated

National Guard helicopters dropped emergency food bundles and bales of hay for people and livestock trapped by snowdrifts as high as rooftops Tuesday after back-to-back blizzards paralyzed the Plains.

At least a dozen deaths were blamed on a weekend storm that knocked out electricity to tens of thousands of people in Colorado, Kansas, Nebraska and Oklahoma and left herds of cattle without food or water. The blizzard spread a blanket of snow on top of the icy layer left by a storm that hit just before Christmas.

Photo Essay: Blizzard Buries the Plains

Because of rising temperatures, many highways were clear, but many rural roads remained impassable, and National Guardsmen used Humvees and snowmobiles to reach people trapped in their homes and take them to shelters.

Colorado also launched a haylift in hopes of saving thousands of cattle immobilized by drifts as high as 10 feet. In 1997, a similar storm killed 30,000 in the state.

"Most of my cattle haven't seen food since last Thursday, when the snow started," said Tony Hall, who has 200 head on a ranch near Lamar, Colo. "Wherever they were standing when the snow piled up, that's where they are now. Every day, it's getting more crucial."

Colorado and Kansas were trying to find enough helicopters capable of hauling hay bales weighing up to 1,300 pounds, said Don Ament, Colorado's agriculture director. Many helicopters in the state's National Guard fleet are in the Middle East.

"These cattle have already gone a number of days without food and water. They're just going to lay over dead if we don't do something soon," Ament said.

Two Huey and three Black Hawk helicopters dropped 400 bales of hay Tuesday to feed cattle in the hardest-hit areas, Colorado officials said.

National Guard helicopters in the state also dropped Meals Ready to Eat, or military rations, just outside people's houses so they could reach the bundles, Sgt. 1st Class Steve Segin said.

In the Oklahoma Panhandle, a dozen troops went door to door in Humvees, checking on rural residents snowed in without power for days. Col. Pat Scully said the priority was to reach people on ranches and farms who might have medical problems.

"We have no reason to believe anybody is hurt, but we did think it was necessary to do some welfare checks," said Michelann Ooten, spokeswoman for the Oklahoma Department of Emergency Management.

Members of the Kansas National Guard and the Highway Patrol helped the Haskell County Sheriff's Department also went door to door.

At least 25 emergency shelters had been set up in western Kansas, said Sharon Watson, spokeswoman for Kansas Emergency Management.

Ice in some areas was even more difficult to deal with than the snow, snapping trees and bringing down power lines. In Nebraska, big portable generators were set up to maintain water service and keep emergency shelters open.

In an aerial tour, Nebraska Gov. Dave Heineman said Tuesday that he saw damage "more massive and more extensive than any of us imagined," noting that in some areas ice was 3 inches thick on trees. Heineman had declared a state of emergency in advance of the storm.

About 22,000 homes and businesses in western Kansas were without power, along with at least 29,000 customers in Nebraska and more than 6,000 in Colorado and Oklahoma. Some utility officials warned it could take weeks to restore electricity.

Every motel in the western Nebraska town of Kearney was full of people who had no electricity.

Patrick Keough, 49, was one of 10 people in his family sharing three rooms at the Kearney Ramada Inn. At his home east of Kearney, there was no power at his house or shop, where he makes fiberglass animals for advertising.

"Hardly anybody got any snow," Keough said Tuesday. "It's all just ice. Even the gravel roads are a sheet of ice, because the gravel is below the level of the ice. I've never seen that in my life."

Power poles are snapped off for miles around, he said, and he was told not to expect any power for at least three weeks.

Ten traffic deaths were blamed on the latest storm in Colorado, Texas and Minnesota. A tornado spun off by the same weather system killed one person in Texas, and a Kansas sheriff's deputy died in his home after falling down the stairs while tending to a generator.