"The people dead from this incident is now 16," said National Disaster Management Unit head Pius Masai.
Authorities had initially put the death toll from Friday's building collapse in the northern district of Huruma at 12 last night.
President Uhuru Kenyatta had yesterday visited the ruins of the building, where residents perished after concrete floors collapsed on top of each other.
Building authorities had condemned the bloc, home to more than 150 families, but the order to evacuate and carry out the demolition had been ignored.
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The collapse of the residential bloc in a torrential downpour prompted questions over the quality of a construction completed only two years ago near a river.
Two neighbouring buildings were declared unsafe and were evacuated.
The downpours were the heaviest since the start of the rainy season and caused flooding and landslides in many areas of the capital.
Elsewhere in the city, two people were swept away in their vehicle in an industrial district, four people died when a wall collapsed and another victim drowned, police said.
Troops were leading operations to rescue dozens of other residents.
Several buildings have collapsed in Kenya in recent years amid a wave of construction -- but building quality has been questioned amid claims that unscrupulous developers have been getting around regulations by paying bribes to local authorities.