Story highlights Grandmother thought she dropped girl off at day care, authorities say

Nearly 30 hot car deaths have been reported this year

(CNN) A 4-month-old girl was found dead in Oklahoma after she was left inside an SUV for most of the day, the Oklahoma County sheriff's office said.

The child's grandmother thought she had dropped off the girl at a day care in the Oklahoma City metropolitan area Friday morning on her way to work, said Mark Opgrande, a spokesman with the Oklahoma County sheriff's office.

The woman, who had custody of the girl, went to pick up her granddaughter around 5 p.m., prompting day care workers to look for the child inside the facility. They couldn't find her, and later discovered her deceased in a car child seat inside her grandmother's SUV, Opgrande told CNN affiliate KFOR.

"She apparently had thought that she dropped off the child this morning, which she had not," Opgrande said.

The girl was in the car all day while her grandmother was at her place of work in Oklahoma City, officials said.