CINCINNATI — The foster parents of a missing 3-year-old developmentally disabled boy were charged Monday with involuntary manslaughter in his death.

Liz and David Carroll Jr. are accused of leaving Marcus Fiesel in a closet in their Clermont County home just east of Cincinnati while they went to a family reunion in Kentucky on Aug. 4, Hamilton County prosecutor Joe Deters said.

Investigators believe the boy was dead when the couple returned home two days later, Deters said. The couple reported the boy missing from a Hamilton County park Aug. 15.

A Hamilton County grand jury indicted the Carrolls on charges of involuntary manslaughter and endangering children, and David Carroll was charged with gross abuse of a corpse.

David Carroll took the boy's body to rural Brown County and burned it, Deters said.

The boy's disappearance triggered an intensive search that brought hundreds of volunteers. Liz Carroll had told authorities that Marcus wandered away from her in a suburban park after she passed out because of a heart condition.

The search, using helicopters and sophisticated high-tech equipment along with hundreds of volunteers, initially focused on a 5-square-mile area of Juilfs Park in Anderson Twp. It was later expanded to other nearby wooded areas and waterways with searchers combing the areas at least five times, according to the Hamilton County sheriff's department.