OKLAHOMA CITY (AP) - A powerful ice storm that has been blamed for at least 15 deaths across the state pounded Oklahoma Sunday, blanketing roads with sleet and ice and knocking out power to more than 122,000 homes and businesses.

Authorities said 12 people died due to collisions on slick highways, and three others apparently died of hypothermia from 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 being withheld pending notification of next of kin.

Later 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. Troopers said the roadway was covered with ice and the vehicle was traveling at unsafe speeds for the conditions.

Also Sunday, Cheyanne Lorraine Carter, 15, of Claremore, died after the pickup in which she was a passenger apparently lost control and ran off Oklahoma 66 about three miles north of Claremore on Sunday.

“The roads are still very slick, said OHP trooper Kera Philippi. “Of course, in these kinds of conditions we encourage people not to travel unless it's absolutely necessary.

Since the storm began Friday, OHP worked more than 200 collisions across the state.

Kevin Rowland, chief investigator for the Medical Examiner's Office, said his office is investigating possible hypothermia deaths in Oklahoma City, Chickasha and Tulsa on Saturday.

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

The roof on a two-story gymnasium at Mid Del Christian School in Del City, located east of Oklahoma City, collapsed Sunday under the weight of ice and snow that had accumulated since Friday, said fire department Capt. Brandon Pursell. The gym was empty and no one was hurt, Pursell said.

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

“We're very concerned about those folks, said Michelann Ooten, a spokeswoman for the agency. “It's definitely a difficult situation for Oklahomans who are without power.

Public Service Company, which provides power to 514,000 customers in eastern and southwestern Oklahoma, said 44,801 customers are without power including almost 16,000 in McAlester in the southeast part of the state, one of the hardest hit areas.

Oklahoma Gas and Electric Co. reported about 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.

Additionally, electric co-ops said the storm had destroyed more than 700 utility poles statewide.

Utility crews from several cooperatives reported up to two inches of ice on power lines in eastern Oklahoma, Ooten said.

“Eastern sections of the state are feeling the greatest impact of these storms, and we're continuing to receive reports of damage and power outages, Ooten said.

On Sunday, Gov. Brad Henry asked President Bush to approve an emergency disaster declaration for all 77 Oklahoma counties to expedite the delivery of federal resources, including generators for public facilities and bottled water for shelters in the communities hit with power outages.

“We're doing everything we can to help Oklahomans who have lost power or suffered other hardships because of the winter storm, Henry said. “State and local authorities and their partners in the private sector are doing a great job responding to this emergency, but we need additional resources that only the federal government can provide.

Amtrak canceled passenger rail service Sunday between Oklahoma City and Fort Worth, Texas, because of a Burlington Northern-Santa Fe freight train that was blocking the tracks.

The final round of wintry precipitation pushed into eastern Oklahoma Sunday afternoon and was expected to clear the state by late Sunday, the National Weather Service reported. But strong northerly winds were forecast , dropping wind chill into single digits.