The walls of the Patel dam, situated on top of a hill in Nakuru county, 190 km (120 miles) northwest of Nairobi, gave way late on Wednesday.
Governor Lee Kinyanjui said Nakuru County was working closely with KRCS as well as the security agencies to coordinate rescue missions.
The rescue teams have managed to retrieve 10 bodies as Red Cross reports it has so far rescued 40 people and rushed them to various health facilities in Subukia and Rift Valley General Provincial Hospital. Thirty-eight people have been confirmed dead, hundreds are believed to have lost their homes and over 2,000 have been displaced by the flooding.
"The extent of the damage has yet to be ascertained", he said.
Police chief Joseph Kioko said, "We have recovered... bodies and many people are missing".
The toll now brings to 152 the number of people who have died countrywide as a result of floods since heavy rains started in March, according to Kenya's Capital FM radio website.
A search-and-rescue mission was ongoing.
The Ministry of Education has closed Solai Boys' High School in Nakuru as it flooded after Patel Dam burst. "Looking at families being displaced, children, mothers, the elderly being swept away by floods, it's traumatizing".
Hundreds of people are said to have been left homeless.
"The county has dispatched ambulances to the scene to aid in the evacuation of victims".
"We urge residents to continue to be vigilant due to flooding caused by heavy rains experienced in the county and other parts of the country", he said.