Witnesses said the matatu was trying to avoid hitting a motorbike when it rammed into the trailer which was coming from Sotik.
Among the dead was a student of Maranda high school who was traveling home, police said.
Those injured are nursing injuries at different hospitals in the region including Keroka district hospital, St. Catherine Ichuni mission hospital, and the Kisii teaching and referral hospital.
Masaba North Police Boss Robert Ndambiri confirmed the incident and urged drivers to be Keen while using the Kisii -Keroka-Sotik road which is prone to accidents due to its narrow nature.