Twin 3-year-old girls were found dead after being left in a hot car in Georgia on Sunday — their foster parents desperately searching for them before making the grim discovery, authorities said.

The circumstances of the tots’ deaths remain unclear — the girls were initially thought to be missing before one of their foster parents called 911, when they were found unresponsive in a vehicle in the backyard of a home, according to the Hinesville Police Department.

A coroner report concluded the two toddlers, identified as Raelynn Keyes and Payton Keyes, died from heatstroke and that the deaths were accidental, CBS affiliate WTOC-TV reported.

The temperature was around 92 degrees Fahrenheit at the time.

The girls’ birth mother, Skye Keyes, said she last saw her daughters Friday with a caseworker — telling WTOC her heart is broken.

“It’s a nightmare. It feels like a giant nightmare,” she said.

Keyes and her husband would see the toddlers each week, saying they lost custody because they were still grieving the premature death of another child.

Hinesville police Capt. Tracey Howard said family desperately searched for the girls when they couldn’t be found inside the home, expanding the search to the backyard and surrounding neighborhood.

The foster parents went home to recheck the backyard and found the girls in the vehicle.

Raelynn and Payton had been living with their foster parents and two other siblings for about a year and a half.

“We’re putting all of those pieces of that puzzle together to try and make a determination of what led to their death,” Howard told WTOC.