The Patel Dam ruptured late Wednesday in Solai, in Nakuru County, about 120 miles northwest of Nairobi.
"Locals at Solai shopping centre talk of a huge explosion" before seeing a cloud of water move their way.
In a statement to newsrooms, area Governor Lee Kinyanjui said 15 ambulances have been dispatched to the scene to evacuate victims.
Kenya Red Cross spokeswoman Noellah Musundi, who was on the ground, said that while rescue efforts were still ongoing, 20 people were confirmed dead and about 450 homes were destroyed.More news: Trump tells West Virginia Republicans Blankenship can not win Senate race
A local television station said 20 bodies had been recovered so far.
People are still unaccounted for and more than 100 homes are affected, the Kenyan news site Standard Digital reports.
"The extent of the damage has yet to be ascertained", he said.
Government statistics released Wednesday showed that more than 220,000 people have been displaced by flooding as heavy rains hit the country after three consecutive failed rainy seasons had left it in drought.More news: Facebook US users still loyal to the social network, research reveals
Death toll reaches 31; NYS, KDF, Red Cross, police and Nakuru County government continue with search and rescue operation, CS Fred Matiangi arrives at the scene.
Recent flooding in the country has already killed more than 152 people and displaced a quarter of a million others.
An area representative Peter Mbae told the Daily Nation "We assure residents that the rescue teams are doing their best to evacuate affected families to safety and assist victims get medical attention".More news: Israel Informed Russia Ahead of Strikes in Syria Following Netanyahu-Putin Meeting
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