A dawn accident has claimed 51 lives along Londiani-Muhoroni road, within Kericho County.
The accident involved a bus bound for Kakamega that was travelling from Nairobi.
According to police, the bus had 52 passengers.
Rift Valley Provincial Traffic Officer Zero Arome says no other vehicle was involved in the accident.
Kericho police boss James Mugera said those who died include 31 male passengers, 12 women and seven children.
The Kenyan Red Cross wrote on Twitter that it had overturned. However more details on the cause of the accident were not immediately available.
Footage from the scene showed the faded red bus lying on its side, the seats and mangled bits of metal exposed to the air with the torn-off roof lying at a distance.
Dozens of people milled around the accident site and goods were strewn over a large area.
President Uhuru Kenyatta called for an investigation into the tragedy.
“My heartfelt condolences to the families of fellow Kenyans who lost their lives in a tragic road accident at Fort Ternan in Kericho County this morning and wish those in hospital quick recovery,” he wrote on Twitter.
“I would like to remind drivers to always exercise caution to avoid such catastrophic incidents.”
Official statistics show that around 3,000 people die annually in road accidents in Kenya, but the World Health Organization estimates the figure could be as high as 12,000.
In December 2017, 36 people died in a head-on collision between a bus and a lorry.
n 2016 more than 40 people died when an out-of-control fuel tanker ploughed into vehicles and then exploded on a busy highway