Three family members in Witbank died of carbon monoxide poisoning, allegedly caused by their heater, Mpumalanga police said on Tuesday.
Seth Offel senior, 38, his wife Rose, 30, and their three-year-old daughter Roseth were found dead on their bedroom floor on July 16, Sergeant David Ratau said.
The couple's four-year-old son was found in the house unharmed.
"The father was found holding the baby girl in a kneeling position on the main bedroom floor, while his wife was found lying next to them," he said.
The incident was believed to have happened on the evening of July 12, or the early morning of July 13.
A colleague of the 38-year-old maths teacher and pastor, who tried to contact him from July 13, went to the house on July 16.
"He knocked on the front door for three days and tried to phone the man but there was no answer," said Ratau.
The family friend went around the house and saw the family lying on the floor through the main bedroom window and called the police.
"The three bodies were already found in the early stages of decomposition," said Ratau.
"[The four-year-old boy] was shivering when we found him."
"It is a mystery how he survived, but police saw that there was food in the house."
The boy was taken to a social worker. Blood samples were taken from the bodies to determine the cause of death.
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Image: Gas room heater from Shutterstock