At least 55 people have died over the past four days in northern and eastern India as a spell of cold weather swept the region, officials said on Monday.
In the northern state of Uttar Pradesh, 24 people have died from biting cold in rural areas, a disaster management official said from Lucknow, the state capital.
Authorities in adjoining Bihar state said they have received reports of 31 deaths over the past four days.
Police said a group of teachers used books meant for poor children in the impoverished state's Gaya district for a bonfire.
"They (teachers) burned some 500 books packed in two gunny bags to get warm," said Hansnath Singh, a senior police officer.
Dense fog in most parts of India has already affected train and flight services, and homeless people can be seen huddling around bonfires after nightfall in the capital, New Delhi, and other cities.
The deaths occurred as nighttime temperatures dipped to 39 degrees Fahrenheit in parts of India, most of which is used to short and mild winters.
Those killed have mostly been beggars or impoverished migrant workers who often sleep in the open, with only plastic sheets or jute cloth sacks for cover.
A 72-year-old woman and her two young grandchildren died when her thatched hut caught fire after she lit a bonfire to keep the family warm in Kanpur, an industrial town in Uttar Pradesh state.
Authorities in Uttar Pradesh decided Sunday to light bonfires of wood and waste cardboard to keep homeless people warm.
The cold spell was likely to continue for at least another week.