A mother hurled her 18-day-old baby girl into a snowbank in south Minneapolis Saturday morning, horrified witnesses told police.

The 21-year-old mother was arrested and is expected to face charges of child neglect and endangerment, said Minneapolis police spokesman Sgt. William Palmer.

"I think you can only call it bad judgment on the mother's part, given what the temperature conditions were," he said. "She made a decision that was completely inappropriate."

The infant, who was wearing only a T-shirt and a blanket in 16-degree weather, was treated for exposure at Hennepin County Medical Center. She was to be released to protective custody after her condition stabilized.

At the time she was taken to the hospital, her body's core temperature was 95 degrees, Palmer said, adding, "It was initially life-threatening." That temperature is generally considered to be low enough to trigger hypothermia.

The woman and a man were fighting near their home in the 1800 block of 11th Avenue S. shortly after 8 a.m. when the man fled and the woman followed him, police said.

About a block north of their residence, at a bridge crossing Interstate 94, the woman threw the child into the snowbank.

A man who was getting off a Metro Transit bus called 911 when he saw what had happened. He took the baby out of the snowbank, but the mother snatched her from his arms and began walking back home.

Witness E. Mandell said the woman threw the baby into the snow "like a major league pitcher in the windup for a fastball. I didn't believe at first it was a baby because no one in their right mind is gonna do that."

Walking on the other side of the street, Mandell said he first noticed a man running, then a woman behind him, also rushing but slower because she was carrying a bundle.

"At first I thought it was clothes or something, because she wasn't handling it the way you would a child. It was kind of rough," he said.

Then, Mandell said, another man walking on his side of the street got his attention and said he thought she had a baby. When she threw down her bundle, neither man could be sure what it was, but the other man called 911 before leaping over the snowbank to check, Mandell added.

"He said, 'Get over here, get over here,' with a lot of emotion in his voice," Mandell said.

About a block away from the house, officers arrested the woman, as well as the man, who is expected to face domestic assault charges, police said.