A 30-year-old woman and her four-year-old son were burnt alive after unidentified men allegedly torched their home at Ruppur village in Birbhum’s Bolpur on Thursday night.

The woman’s husband has been critically injured.

Police have started a murder case following a complaint from a family member of the victims and are investigating whether there was any foul play involved.

“We have started a probe following a complaint lodged with us. No one has been detained or arrested so far,” said Birbhum superintendent of police Raj Narayan Mukherjee.

According to local residents, Rupa Biwi, 30, her younger son Ayan Sheikh, 4, and her husband Abdul Alim, 38, were sleeping in their one-storey house. Wasim Akhter, the couple’s 15-year-old son, who was sleeping in another room, was the first to inform the neighbours about the fire. The police have been interrogating him as well.

While Rupa and Ayan were declared dead at Bolpur sub-divisional hospital, Abdul was admitted to Burdwan Medical College and Hospital in a critical condition.

The family members claimed that they suspected someone had sprayed kerosene or petrol through the window and set the house on fire using a tree branch.

“It is a case of murder and we want a thorough probe to find the culprits who are behind the deaths of my daughter and her son,” said Sheikh Karim, Rupa’s father.

A police officer claimed there were several missing links to the case and they had asked for a forensic team.

“We will conduct a forensic test to determine whether the fire was actually set from outside or inside,” the police officer said.