Two people died when a matatu collided with a truck on Sotik-Keroka road in Nyaronde, Nyamira County, on Wednesday morning.
The driver of the matatu died at the scene while the other victim was declared dead on arrival at St Clare's Kaplong Mission Hospital in Bomet County.
A doctor at the facility said another victim was in critical condition.
Nyamira County Commissioner Amos Mariba said they were yet to confirm the total number of casualties.
However, eight other people were admitted to Longisa Hospital, also in Bomet.
They were initially taken to St Clare's but were transferred for advanced treatment.
Officers from Bomet's disaster management department responded to the incident that took place at about 8.30am.
Mr Stanley Mutai, a senior disaster management officer, confirmed that eight casualties were taken to Longisa.