Shinti Devi and her three minor children were set on fire late Wednesday night in Arnia village in Vaishali district, which is about 40 km from here.
A case has been lodged against the woman's husband and in-laws on the basis of her statement, a police official said.
According to the woman's statement, the husband and in-laws first locked her along with the children in a room, beat her and then set them ablaze for allegedly stealing her sister-in-law's jewellery.
She was rescued by her neighbours after they saw fire and smoke in her house and informed the police.
The woman sustained serious burn injuries.
"She was referred to Patna medical college and hospital for treatment after her condition deteriorated," the official said.
The accused are absconding since the incident.
