Passers-by found the 42-year-old woman and her 14-year-old child unconscious in the BMW, which was parked in front of a school with the engine running, and alerted police at about 10pm.

Johor Bahru Utara police chief Balveer Singh said the results of an autopsy were still pending.

Based on a preliminary investigation, police suspect their deaths were caused by a leak in the engine’s petrol line, which could have led to carbon monoxide poisoning.

“We found that the victim’s last conversation was in a WhatsApp group with her friends, where she told them she had finished shopping in the area and was stopping by the road because she was not feeling well,” said Balveer.

“The victim, a mother-of-three, lives in Bakar Batu,” he added.