(NBC News Channel) — Authorities say a 5-year-old child has died after being left in a hot car for several hours in Houston, Texas.

The Harris County Sheriff’s Office responded to a home in the Summerwood area around 3 p.m. Monday.

Officials said the child, a sibling and their mother had returned home after running errands. Two to three hours later, the mother noticed the 5-year-old was not inside the home and began looking for him. She checked her car and found the 5-year-old unresponsive. He was still buckled in a car seat.

The mother called 911. Paramedics responded and the child was pronounced dead at the scene.

The mother told authorities the child knew how to unbuckle themselves from the car seat, and had done so before. They also said the family was driving a rental vehicle, but it’s unclear if that was a factor in the boy’s death.

An investigation is ongoing.