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 Uttar Pradesh, 24 people have died from biting cold in rural areas, a disaster management official said from Lucknow.
Authorities in adjoining Bihar 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.