The body, stuffed in a plastic bag, was found last night after the foul smell from the sewer tank of a building in Munirka became unbearable, police said.
The building houses 31 rooms, that have been rented out to students and professionals, they added.
After it was found that the foul smell was emanating from the sewer tank, a PCR call was made, police said.
When the lid of the sewer tank was opened, the headless body of the woman was found stuffed inside a black-coloured bag.
Police is trying to establish the identity of the woman.
They are preparing a list of the residents of the building. They are also trying to contact people whose female members have bee reported to be missing in the last few days.