Former Congress lawmaker Siricilla Rajaiah's daughter-in-law and three grandchildren were burnt to death after a fire broke out at his residence early on Wednesday morning in Warangal city of Telangana.

A leaking gas cylinder caused the fire, which killed Sarika (Rajaiah's daughter-in-law) and her three sons – Abhinav, 7, Ayan, 3, and Sriyan, 3. The fire took place on the second floor of Rajaiah's residence in Hanamkonda area of Warangal city.

"Most probably the fire was due to gas is too early to come to a will take some more time...there is no clarity," a senior police officer told PTI.

Sarika married Rajaiah's son in 2002. She had reportedly filed a dowry case against her in-laws in April last year, a month after allegedly attempting suicide,NDTV reported.

Telangana police have initiated an investigation into the incident. They are looking into all possible angles.

Meanwhile, Sarika's family members in Nizamabad district have expressed doubt on the reason behind the accident. They claimed that it could not be a fire accident and also ruled out any possibility of suicide, IANS reported.

After the death in his family, Rajaiah has told the party leadership that he is opting out of 21 November by-election to Warangal Lok Sabha constituency. Rajaiah had filed the nomination for the by-elections on Monday.