Twin sisters died of suffocation here after they got their house sprayed with pesticides and slept at night without ventilating the poisonous fumes, police said on Monday.

The 54-year-old unmarried sisters —— Usha and Sandhya Nadkarni —— were found dead at their residence on Friday after a milkman, unable to get a response in the morning, alerted the housing society members who summoned police.

When fire brigade men opened the door, strong smell of pesticide spray repulsed them. After re-entering the house after wearing a mask, they saw the deceased lying in a bedroom and the hall.

A post-mortem report confirmed the death by suffocation and inhalation of poisonous gas, police added.

The sisters, after pest control operation in the morning, reportedly spent the day at a relative’s place and returned home late at night. They went to sleep without opening the windows and ventilating the harmful gases in the house.

A woman medical college student, who resided with the Nadkarni sisters as paying guest, had gone to stay with her friend in view of the pest control.