In sub-zero winter temperatures, Amba Bohora, 35, and her sons aged seven and nine, are believed to have constructed a small fire inside a tiny wooden hut close to their home in rural western Nepal. By the morning all three were dead.
"They are suspected to have died from smoke inhalation," Uddhab Singh Bhatt, the area's senior police officer, told CNN.
Bohora was taking part in chhaupadi, a common practice in the west of the country in which women, considered unclean during menstruation, are forbidden from touching other people, food that may be consumed by others, cattle and even books.
They are confined to a small structure, called a menstruation hut, where women are expected to sleep every night, even during Himalayan winters.
"She had lit a fire inside the shed to keep warm and it appears the blanket had caught fire while they were asleep filling the room with smoke," said Bhatt.
"We had been making good progress in our district in terms of rooting out this custom. We had in fact believed that chhaupadi was no longer practiced in Bajura, and that all the huts had been destroyed," Chetraj Baral, head of the Bajura district administration where the incident took place, told CNN.
According to the legislation, anyone found forcing a woman into a menstrual hut will be sentenced to three months imprisonment or a $30 fine.
Activists believe that the formulation of a new law will not be able to end the centuries-old ritual.
They say menstruation needs to be destigmatized in society, and men and women alike need to be educated about the potential dangers of the tradition.
Authorities are considering whether to charge Bohora's family under the 2018 law, according to Baral.