A 14-year-old boy died during his sleep in the central province of Quang Binh after his family burned charcoal to heat their room the whole night.
His mother and sister are receiving medical treatment, Tuoi Tre reported.
On Monday evening, Pham Thi Huong and her children burned charcoal in an open burner and closed the room’s door and windows before going to sleep. The outside temperature was around 10 degrees Celsius.
The following morning, their neighbors went into the house and found the three lying motionless.
The three were rushed to a local hospital.
Huong's 14-year-old son died on Tuesday afternoon. Her condition is critical.
Doctors said the three victims suffered from inert gas asphyxiation, after burning charcoal in a closed room for a long time.