A tragic incident unfolded as a three year old boy was found dead in his stepmother's car, after she allegedly forgot he was asleep in the back seat during sweltering 31C heat.

The dehydrated body of Miguel Antunes Versari was discovered in the red Chrysler after being left for over 10 hours. His mother's partner reportedly forgot to drop him off at nursery school when he fell asleep in the vehicle.

She was supposed to leave him at the nursery in Videira, Brazil, at 7am on April 25. However, after dropping her wife - Miguel's mother - at work, she forgot about the young boy and left him in the car.

The horrifying discovery of the boy's body was made when she prepared to pick him up from the nursery. During the peak of the day, the outside temperature in Videira reached around 31C. Inside a car under such conditions, temperatures could soar to over 57C - akin to a warming oven, reports The Mirror.

Police have launched an investigation into the suspicious death and are questioning Miguel's stepmother.

A police spokesperson revealed the day after the devastating discovery: "Yesterday, she said that the child had flu-like symptoms and was medicated with ibuprofen. So he was not as active as usual and was sleeping in the back seat of the vehicle. After leaving her partner at work, she did not realise that the child was sleeping."

Authorities are awaiting an autopsy report to determine the exact cause of the boy's death and are reviewing CCTV footage from around the family home.