The 4am accident involved a bus bound for Kakamega that was travelling from Nairobi.
The number of people known to have died from the Wednesday morning bus accident in Kericho has risen to 50, according to police.
According to police, the bus had 52 passengers.
POLICE and NTSA looking for 3 directors of the killer bus that left 51 people dead in Londiani accident this morning. pic.twitter.com/4NbRD7BW6M
— CapitalFM Breaking News (@BreakingNewsKE) October 10, 2018
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.
LIVE: Reaction to the death of 50 people in a road crash at Fort Ternan in Kericho. https://t.co/CWnLoTRp3o
— NTV Kenya (@ntvkenya) October 10, 2018
Dozens of people milled around the accident site and goods were strewn over a large area.
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.
In 2016 more than 40 people died when an out-of-control fuel tanker ploughed into vehicles and then exploded on a busy highway.