The burst happened in Solai, Nakuru county, 190 kilometres northwest of the capital Nairobi, officials say,
The death toll from flooding caused by a burst dam wall in Kenya's Rift Valley rose to 47 on Thursday and could go higher as more bodies are pulled from the mud, the local police chief said.
"So far it is 47 dead. We are still on the ground," Japheth Kioko, the police chief for Rongai division, told Reuters news agency.
The dam in Nakuru county burst late on Wednesday, affecting as many as 2,000 people.
It happened after weeks of heavy rain, causing "huge destruction" and deaths, a government official said on Thursday.
TRT World's Adesewa Josh reports.
The dam gave way in Solai, in Nakuru county, 190 kilometres northwest of Nairobi, late on Wednesday.
"The water has caused huge destruction of both life and property. The extent of the damage has yet to be ascertained," Lee Kinyajui, the governor of Nakuru, said in a statement.
Kenya Red Cross said on Twitter it had rescued 39 people so far.
39 people taken to hospital last night after Patel Dam in Subukia, Nakuru County, broke its banks affecting nearby villages. Search and rescue efforts by County Government, Kenya #RedCross Society and @Ems_Kenya ongoing.— Kenya Red Cross (@KenyaRedCross) May 10, 2018
Kenya, like other countries in East Africa, has experienced heavy rain over the past two months.
The government said on Wednesday the rain had killed 132 people and displaced 222,456 in 32 counties since March.