Mamata Dutta?s walking aid stands mute witness to the fire that gutted her room and claimed her life on Thursday. Pictures by Sanjoy Chattopadhyaya

An elderly widow, locked in by family members while they were away, was burnt to death when the flat caught fire on Thursday morning.

Police are yet to ascertain the cause of the fire.

Neighbours rushed over as soon as they saw smoke billowing out of the second-floor flat off Beleghata Main Road, but could do nothing as the grille gate was locked from both outside and inside.

By the time the locks were broken and firemen entered the flat, 72-year-old Mamata Dutta, crippled from a stroke suffered a year ago, was dead. Everything in her room was gutted.

Deputy commissioner of police (eastern suburban division) Vineet Goyel said Mamata lived in the rented apartment in Gopi Kanan with son Monimoy, daughter Babli, daughter-in-law and grandson. ?Early in the morning, Monimoy and his wife left with their son for Sarisha Ramakrishna Mission. Babli had gone for tuition.?

Surojit Sarkar, who lives next door, lamented that neighbours could have saved their mashima had the gate not been locked.

?We had asked Bappada (Monimoy) several times not to lock her up in the flat while they were away. Even she (Mamata) had lodged a police complaint against this practice of her son a few years ago,? said Sarkar.

Confirming Sarkar?s claim, additional officer-in-charge of Beleghata thana Gautam Kumar Kar said police had warned Monimoy not to lock in his mother. Monimoy claimed that he did lock the gate from outside when he left home in the morning with wife and son, but denied any knowledge about the other lock. The keys to the lock were with his sister, wife and a domestic help, he added.

Kar said Mamata had suffered a mild stroke a year ago and partially lost mobility and speech. ?She would even take a long time to move from her bed to the bathroom with the help of her walking stick.?

Police are not sure whether the domestic help, who usually comes around 11 am, turned up on Thursday. ?We have not been able to talk to her. Some said she was there around 8.30 am, when Mamata?s daughter left for tuition, while others claimed she had not turned up today,? Goyel said.

According to fire department officials, local residents noticed the smoke around 10.25 am. ?They alerted us around 10.35 and we reached the spot in 15 minutes with two tenders,? said an official.