The boy was found dead Monday in the searing blacktop parking lot of South DeKalb Mall, police said.

The grandmother told DeKalb County police she did not realize until she returned to her car at the end of the day that she had forgotten to take him to his day-care center, Sgt. J.W. Conroy said.

Police said heat could have been the cause of Hezekiah Silvester Welch's death, but added that they would not know for sure until the Medical Examiner's Office completes an autopsy.

They said there were no signs of trauma on the boy's body.

The boy's grandmother, Deborah Welch, was questioned and released Monday night without being charged, according to police, who said the investigation is continuing.

Police identified her as a Lithonia resident, in her early 40s, who works at the Social Security office inside the mall on Candler Road.

She usually drops the boy off at a day-care center on nearby Flat Shoals Road, police said.

Police Capt. Paul Taylor said authorities did not know why the grandmother, who has custody of the child, did not leave him in day care Monday.

Taylor said the grandmother reported to work at 7:30 a.m. and apparently did not check on the child during the day.

She told police she found the boy unconscious after work when she returned to her black 1999 Pontiac Grand Am, parked just outside the office, he said.

"As far as we know, she discovered the child in the car after she checked out at 4:15 (p.m.)," he said.

Once she found Hezekiah, she ran back into her office and co-workers called 911, police said.

The same building where the grandmother works houses a DeKalb police mini-precinct.

Despite vehicular and pedestrian traffic in the parking lot of the busy mall throughout the day, nobody reported seeing the boy in the car, police said.

Police would not guess at the heat in the car. Though Monday started cool, with a low in the 60s, the temperature climbed to near 90 in the afternoon. Inside the closed car on the baking pavement, it would have been far hotter.

The whereabouts of the boy's mother was unknown. A man came to the scene late Monday identifying himself as the child's father, and was taken away by police.

If heat-related, Monday's tragedy would be the second of its kind in metro Atlanta in a little over two years. In June 1998, 3-year-old Samuel Oh of Doraville died when a day-care worker accidentally left him alone in a van in Tucker for more than two hours on a 95-degree day.

The boy's family later filed suit against Ford, the maker of the van, contending that it had a moral responsibility to build into its cars and trucks an automatic ventilation system that would hold down the heat.

State Sen. Donzella James (D-Atlanta) during the last legislative session failed to win passage of a bill that would make adults responsible if children they left unattended in vehicles died. She has said she intends to reintroduce the bill next year.