OKLAHOMA CITY (AP) - President Bush declared a federal disaster in Oklahoma in the wake of an ice storm that has killed at least 15 people and knocked out power to more than 122,000 homes and businesses.

Residents in southeastern Oklahoma and other hard-hit areas of the state were without power for a third straight day Monday amid subfreezing temperatures, and authorities said it could be up to a week before power is fully restored.

“Very, very few people have electricity, said Undersheriff Richard Sexton of Pittsburg County, where almost 16,000 homes and businesses were without power in McAlester and surrounding areas late Sunday.

Sexton said the devastation following three days of freezing rain that coated tree limbs and power lines with thick coats of ice was reminiscent of a devastating ice storm in December 2000 that knocked out power to more than 170,000 electrical customers statewide.

“Tree limbs and power lines are snapping. We've run into situations where the roads have been blocked, Sexton said. “It's kind of caused people to go into panic. They're struggling to try to get heat, to get electricity to their houses.

He said the county jail is operating on emergency generator power and that many other public facilities are relying on generators to stay open.

Emergency workers are finding shelters for elderly residents and others with medical conditions who are without power, Sexton said.

“I've seen a lot of the community start to come together and try to provide for those who don't have a place to stay, he said.

The Oklahoma Department of Emergency Management said utility crews worked throughout the night to restore power.

“Everyone's working as hard and as diligently as they can. We understand how difficult it must be for people who don't have power, said Michelann Ooten, spokeswoman for the agency.

Late Sunday, President Bush approved Oklahoma's request for a federal emergency disaster declaration. Gov. Brad Henry requested federal aid after it became clear the state would need federal support to recover from the statewide storm.

“We appreciate President Bush's quick response to our request for help, Henry said. “The federal aid will help us deliver assistance to the tens of thousands of Oklahomans who have lost power or suffered other hardships because of the winter storm.

The disaster declaration covers direct federal assistance as well as 75 percent reimbursement for emergency protective measures by local and state personnel.

Authorities said 12 people have died due to collisions on slick highways since the storm struck on Friday, and three others apparently died of hypothermia following prolonged exposure to bitterly cold temperatures.

Seven people were killed before dawn Sunday near Elk City when the minivan they were riding in hit a slick spot along Interstate 40, crossed the median and slammed into an oncoming tractor-trailer, the Oklahoma Highway Patrol reported.

The names of the victims, which included six men and a woman, were withheld pending notification of next of kin. Troopers said all were residents of Mexico, but their immigration status in the U.S. had not been determined.

Also Sunday, Britton Kannady, 51, of McAlester, was killed when he lost control of his minivan on U.S. 75 in Tulsa County, struck a culvert and overturned, coming to rest in a creek, the patrol said. Cheyanne Lorraine Carter, 15, of Claremore, died after the pickup in which she was a passenger apparently lost control and ran off Oklahoma 66 near Claremore.

Kevin Rowland, chief investigator for the Medical Examiner's Office, said the bodies of three people were found in Oklahoma City, Chickasha and Tulsa on Saturday, the apparent victims of hypothermia.

“They were found dead out in the cold, Rowland said. Rowland did not have the names of the victims but said one was elderly and two apparently were transients.

A wind chill advisory is in effect for parts of Oklahoma through Monday. Forecasters said gusty winds will drop wind chill indices to the teens and single digits.

Statewide, 122,338 electric customers were without power Sunday night, mostly in eastern sections of the state, OEM said.

Public Service Company, which provides power to 514,000 customers in eastern and southwestern Oklahoma, said 44,801 customers were without power. Oklahoma Gas and Electric Co. reported 19,000 customers without power, including about 10,000 in Muskogee in eastern Oklahoma.

The Oklahoma Association of Electric Cooperatives said 58,550 coop customers were without power as up to four inches of freezing rain and brisk winds in eastern Oklahoma took a heavy toll on power lines and utility poles.

Electric coops said the storm had destroyed more than 700 utility poles statewide.

The storm caused flight delays and cancellations at airports in Oklahoma City and Tulsa. Amtrak canceled passenger rail service Sunday between Oklahoma City and Fort Worth, Texas, because of a Burlington Northern-Santa Fe freight train that blocked the tracks.