The Cottage Grove girl was found about 5:30 p.m. Wednesday, Middleton Police Sgt. Charles Foulke said.

Police said the mother was sleep deprived and under a great deal of stress. She apparently forgot to drop the child off at day care Wednesday morning before going to work at Pleasant Co. in Middleton, Foulke said.

``She just forgot, as hard as that is to believe,'' he said. ``It really sounds like it was a tragedy.''

The baby was in the car from 9 a.m. until about 5:30 p.m., officials said.

An autopsy was scheduled for today, Dane County Deputy Coroner Kurt Karbusicky said.

Karbusicky could not say whether heat was a factor in the child's death. The high temperature in nearby Madison Wednesday was 79, according to the National Weather Service.

Authorities had not released the child's or mother's name because they were still notifying relatives of the baby's death, Karbusicky said.

Dane County District Attorney Brian Blanchard said Wednesday no one was in custody and his office would review the circumstances of the death today before deciding if charges would be filed.

The baby's father went to his daughter's day care Wednesday afternoon to pick her up but was told the girl had not been dropped off, Foulke said. The man immediately called his wife who rushed out to her car.

She found the baby dead and became hysterical, Foulke said. A co-worker saw her and called 911.

The mother hadn't slept much Tuesday night, because the couple's other child - a 2-year-old son who is severely developmental disabled - spent his first night away from home at the Central Wisconsin Center for the Developmentally Disabled, Foulke said.

The mother called to check on her son about 2 a.m. and found he was awake crying, Foulke said. She then drove to Madison to stay with him until he fell asleep.

She returned home around 5:30 a.m. and fell asleep for an hour or two before getting ready for work, he said.