According to a report by Hop Ly Commune People's Committee, people came to the house of Mai Van and his wife Phan Thi at 10 am on February 1 after they could not make contact.
They found the 53-year-old man and his 50-year-old wife unconscious in their bedroom.
The man was dead already while the woman was in critical condition and was rushed to the hospital.
At the site, local authorities found a stove burning coal inside their room.
Doctors at the Thanh Hoa Provincial General Hospital said the woman was suffering from a poisoning associated with carbon monoxide that can be produced when coal is burned with insufficient oxygen.
Last week, a couple and their five-year-old child in the northern province of Bac Giang also died from carbon monoxide poisoning while burning coal to keep warm in their bedroom.