It was during the sweltering climax to the summer's second major heat wave Monday when a woman in the little northwestern Minnesota town of Osage made a frantic 911 call:

She'd just found her 3-year-old daughter unconscious in the family's car in the driveway under a blazing afternoon sun, with the outside temperature pushing 100 degrees.

The little girl apparently shut herself in the car after getting up from a nap sometime after 1 p.m. and wandered outside.

She'd taken a video game with her. It was after 2:30 when her mother found her.

Authorities estimate that the temperature inside the vehicle was at least 130. Roger Wilson, chief of the nearby Carsonville volunteer fire and rescue department, had looked at the thermometer shortly before the call came in. It said 98.

As he neared the house he saw a knot of people around the lifeless girl. "She was out of the car and in the grass," he said. "Bystanders were already doing CPR. Some neighbors were involved."

But despite their efforts and those of the emergency medical technicians who took over, the girl could not be revived and was pronounced dead at the scene.

Becker County Sheriff Tim Gordon withheld the names of the victim and her family, saying authorities need to complete their investigation, which includes the county Human Services Department because the mother runs a licensed day care operation in Osage, a town of 774 about 10 miles west of Park Rapids.

The Park Rapids Enterprise newspaper, citing pending funeral arrangements, identified the victim as Katherine Lynn (KateLynn) Larson, daughter of Mark and Bridget Larson.

A Yellow Pages ad identifies Bridget Larson's business as Bridget's Precious Angels Family Daycare.

The victim's two brothers and one other child were in the house at the time she died, Sheriff Gordon said.

It's been difficult for investigators to even question the mother because she "has experienced a huge amount of trauma," he said.

The investigation wouldn't include an autopsy, Gordon said, because "the family has been through enough" and because there's no reason to question that the death was anything but an accident.

He said authorities don't know why the toddler couldn't get back out of the car. He said that the Mercury Tracer, a "loaner" the family was using temporarily, was unlocked and that a child safety lock lever was deactivated.

"We don't know if she laid down for a nap, succumbed to the heat, or if she even tried to exit the car," Gordon said. "I think we had a child doing what children do. Toddlers are very inquisitive."

Heat effect

According to a study published last year by the American Academy of Pediatrics, the interior of a vehicle left in 93-degree heat can rise to 120 degrees in just 20 minutes and 135 degrees after an hour.

The effect is nearly the same with the windows cracked, the study found.