Four people were pulled alive Thursday from the rubble of an apartment block that collapsed six days ago when heavy rains hit Nairobi, causing floods and landslides in the Kenyan capital.

There were cheers and shouted prayers from the crowd gathered at the site of the ruined six-storey building as a woman, covered with a blanket and lying on a stretcher, was carried to a waiting ambulance.

She was hauled between thick concrete slabs and a tangle of twisted metal after being located by rescuers who gave her oxygen while they continued efforts to extract her.

Later in the day three more people, two women and a man, were pulled from the rubble of the shattered building.

The rescues came after a baby girl was found alive on Monday, more than 80 hours after the building collapsed on Friday night.

Officials have so far confirmed a death toll of 33 from the disaster, but at least 80 more people are believed to be missing and rescuers are now trawling the filthy river nearby for bodies.

Pius Masai of Kenya's National Disaster Operation Centre said the rescued woman was conscious and talking when she was found.

- Rabbits rescued -

He said he had been confident more people could be rescued after several live rabbits were found in the rubble on Tuesday.

"I told you the day we got nine rabbits alive from this place I was sure we will get more people alive," Masai added.

The woman is receiving treatment and assessment of her injuries at Nairobi's main Kenyatta National Hospital.

"I am glad we got her out safely and that is our determination, to pull out as many people as possible who are still trapped under the rubble," Masai said.

He said rescuers decided to extend the search to Nairobi River "because there is every indication that some people may have drowned in the river after jumping out (of the building)".

Seven-month old Delarine Saisi was found on Monday dehydrated but without visible physical injuries in what her father said was a miracle.

But tragedy followed when the girl's mother was found dead late Wednesday.

Another seven people died in several areas of Nairobi after the heavy rains and floods hit on Friday.

Two brothers who own the Nairobi building and three construction officials 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.

But an evacuation order for the structure, which was built next to a river just two years ago, was ignored.

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 ordered the demolition of other buildings deemed illegal or unsafe.