Officials suspect three people who were found dead in their house in central Vietnam on Monday died of smoke inhalation since they were burning coal to keep warm.
Tran Tho Vu, 26, was found dead with his wife, Nguyen Thi Thao, and his mother, Than Thi Phuong, in a 10 square-meter room, news website VietNamNet reported.
Phuong lived nearby and came to take care of Thao, who just gave birth, and the three-day-old baby. The baby survived but was breathing heavily when found.
The family was discovered at 8 p.m. on Thursday when Vu's father came to check on them.
Two pots of burnt coal were found in the room, and the doors were all closed.
Police are conducting forensic tests to investigate the death, but they said the only cause they noticed so far is smoke from the coal.
There is a Vietnamese tradition to burn coal to warm newborns and women during their postnatal period.