The father of an 11-year-old girl who died after trying to walk 10 miles in knee-deep snow on Christmas Day to see their mother has been charged with murder.

Sage Aragon and her brother Bear were with their father when their truck got stuck in a snowdrift in sub-zero temperatures. Robert Aragon let them out to walk to see their mother.

After the alarm was raised searchers found Bear alive in the bathroom of a rest area, 7.2 kms (4.5 miles) from where the children set out. He had hypothermia and was wearing only long underwear. Delusions from the hypothermia had made him discard his jacket, trousers and tennis shoes.

In the early hours of the next morning search and rescue dogs found Sage unconscious and covered in snow by a barbed wire fence. She was wearing a coat, shirt, pink pyjama bottoms and snowboots. She was pronounced dead in hospital of suspected hypothermia.

Bear told rescuers that he and his sister had separated after she decided to try to get back to the truck near state Highway 75, north of Shoshone in south central Idaho, according to the Lincoln County sheriff's office.

Mr Aragon, 55, has been charged with second-degree murder and felony injury to a child and is being held in jail on a $500,000 (£343,000) bond.

Deputies said Mr Aragon let his children get out and walk after his 1988 Buick Century truck stuck in a snow drift on West Magic Road at about 9am on Christmas morning. The authorities said the road was unpassable because of snow drifts. But the official search did not start until police were called by the children's mother JoLeta Jenks, at about 7pm.

Mr Aragon, who had custody of the children and lives in Jerome, told authorities he thought their mother, who was staying in West Magic, was going to meet the children on the road, court papers showed.

Mr Aragon's cousin Kenneth Quintana, 29, who was a passenger in the vehicle, said Mr Aragon did not kill his child. "I feel that Bob was wrongfully accused of murder," Mr Quintana said. "There's no way that he could have known what was going to happen."

Mr Quintana described how he and Mr Aragon stayed behind to free the vehicle and then searched for the children for at least four hours with towels wrapped around their heads. They stopped as hypothermia set in. He said he had no cell phone reception in the search area.

'They found her (Sage Aragon) a mile and a half from where I turned around," Mr Quintana told the local Times-News publication. "If we had kept going, we could have gotten her in time. I just couldn't go anymore, I was so tired. The whole time, we were yelling for the children, our eyes and throat were wind burnt."

Mr Quintana also said he thought Mr Aragon and Ms Jenks had coordinated a plan over the phone for her to retrieve the children.

"We thought their mother was going to meet up with the children," Mr Quintana said. "Where was she? How were we supposed to know she wasn't coming?"

"He didn't send those kids out there to die. He just wanted their mother to spend Christmas with them."

But Ms Jenks told the Times-News she did not receive any call and did not have a car. She said she called police after getting through to Mr Aragon when he returned to his home in Jerome.

In a short hearing on Monday Mr Aragon appeared before a judge where he was given a public defender and a pretrial hearing was scheduled for January 7.

He banged his head on the defendant's table as the charges were read against him. After the judge noted that second-degree murder carries a maximum penalty of life in prison, Mr Aragon said: "Oh my God," as he banged his head on the table.

Ms Jenks told police she became concerned after no one arrived at her home on Christmas Day. She described how her son had separated from his sister as they struggled through the snow. "(Bear) kept on telling her: 'Let's go, Sage, let's go, Sage,'" she said. "She said, 'No, I'm going back.'"

The girl was found about 4.3kms (2.7 miles) from where the two set out, barely visible under windblown, drifting snow when search dogs located her at about 2am on Boxing Day.

She was pronounced dead at a Ketchum hospital; preliminary autopsy results indicated she died of hypothermia. Officials say temperatures in the area at the time the girl was missing ranged from -2.7C (27F) to -20.5C (-5F).

Blaine County sheriff's office said when the call came in to say the children were missing a deputy and a snow plough headed out to look for them but they too become stuck after hitting a snow drift and sliding off the road.

Blaine County Search and Rescue then set up on West Magic Road with one vehicle and two snowmobile teams. The snow had drifted to four feet in places and deputies had to crawl over the drifts to reach the rest area and retrieve the boy. A search and rescue dog team was also deployed which then found Sage.

"Sage was just starting to grow up," Ms Jenks said. "I don't know why this had to happen."

Times Recommends

• 'New York has lost its edge'
• Copenhagen will fail – and quite right too
• More than 17,000 new underwater species found