People in Nairobi have been asked to leave their homes near a six-storey building that collapsed in heavy rain, killing at least 10 people.
Kenyan President Uhuru Kenyatta visited the disaster site and said the building's owners should be arrested.
A baby was among 134 people pulled from the rubble and rescuers are searching for more people who may be trapped.
The buildings to be evacuated house 1,000 people and are built next to a river bank.
The Red Cross criticised "chaotic scenes" as rescuers arrived after the Friday night collapse. Nairobi's police chief has said rescue teams were delayed on their way to the scene by hours-long traffic jams caused by flooded roads.
Rainfall has caused landslides, washed away houses and flooded roads. Police said 17 people died in the Nairobi rains, including those in the collapse. Another four died when a wall toppled over and two were swept away by flood waters.
The building took three months to construct, the BBC's Emmanuel Igunza reports from Nairobi. County authorities say it had been earmarked for demolition and did not have a certificate of occupation that would allow tenants to rent the 119 rooms out.
"The building went down during the heavy rains, but we still want to establish if all the procedures were followed when it was constructed," Nairobi's deputy governor Jonathan Mueke told reporters at the scene.
He said the building, reportedly built two years ago, did not have planning permission.
Across the city, more than 800 homes were affected by the flooding, Kenya's Red Cross said.
Huruma is a poor district on the outskirts of Nairobi made up of narrow streets, meaning firefighters struggled to get to the scene and were delayed by crowds.
After some time, the army took charge of the rescue with the help of the Kenyan Red Cross.
"It appears that some people are getting impatient but... we have got indications that there are people who are still trapped in the rubble," said Nathan Macharia Kigotho, the director of the national disaster operation centre.