A woman was pulled out alive Thursday from the rubble six days after a building collapsed when heavy rains hit Kenya's capital Nairobi.

The woman was pulled out hours after being located on Thursday morning by rescuers who gave her oxygen while they continued efforts to extract her from the ruins of the six-storey building.

Pius Masai of Kenya's National Disaster Operation Centre said the woman was conscious and talking when she was found and complained of debris falling on her during the days-long rescue operation.

She was put in an ambulance, and Masai said she would be taken to hospital and assessed for injuries.

On Monday a seven-month-old baby girl was found alive more than 80 hours after the building collapsed on Friday night. Her father called the rescue a miracle, but tragedy followed when the girl's mother was found dead late Wednesday.

Seven-month-old Dealeryn Saisi was found sleeping in a basin wrapped in a blanket.

READ: Baby girl rescued four days after Kenya building collapse

On Wednesday, rescuers said there was hope of finding more survivors after nine rabbits were pulled alive from the debris.

Officials have so far confirmed a death toll of 33 but at least 80 more people are believed to be missing. A total of 137 people have now been rescued.

Two brothers who own the Nairobi building have been released on bail while investigators gather evidence against them ahead of an expected prosecution.

Located in the poor, tightly-packed Huruma neighbourhood, the building, which housed around 150 families crammed into single rooms, had been slated for demolition after being declared structurally unsound.

Several buildings have collapsed in recent years in Nairobi and other Kenyan cities, where a property boom has seen buildings shoot up at speed, often with scant regard for regulations.

On Thursday Nairobi officials began demolishing other buildings deemed illegal or unsafe.

Additional reporting by Stella Cherono.