Forty-year-old Karapan, his wife Mani (35), their sons Kali Morti (18) and Vangresh (14) are suspected to have died of asphyxiation caused by an angithi kept in their one-room tenement late last night.

While Karapan, Mani and Kali Morti, who were rushed to the General Hospital, Sector 16, were declared brought dead, Vangresh was rushed to PGI where he died after sometime.

While Karapan, Mani and Kali Morti worked with the PWD Department as labourers, Vangresh was a Class VI student at a local Vishav Public School.

"We had seen the family going inside their house around 9.30 pm. Karapan used to unlock the cycles of his neighbours at 5 am every day. When we saw that the cycles were locked at 7.30 am, we grew suspicious and knocked at their door," said Viraswami, a neighbour.

When Karapan did not open the door, they entered the house through the terrace only to find the family members lying unconscious. "We informed the police and all four of them were rushed to hospital. Karapan's two other sons, Murgan (22) and Mani Kandan (18), who are in Chennai, have been informed and are on their way to the city," said Panniamma, a neighbour of the family.

While suffocation is being looked at the cause of death, police are not ruling out the possibility of poisoning. "While the half-eaten dinner was lying on the bed, all family members were foaming at the mouth. The case is being investigated,” said SHO Hari Kumar.