Five people - two men, two children and a woman - died in an early morning accident at Kipsoen near Longisa along the Bomet-Narok highway on Thursday.
Two passengers were admitted to Tenwek mission hospital in critical condition.
Thirteen others suffered minor injuries and were treated at Longisa hospital.
Police said the 14-seater Egesa matatu heading to Kisii from Nairobi was carrying 20 passengers.
Witnesses said the driver lost control of the vehicle as he tried to avoid head-on collision with an oncoming car while overtaking.
Police in Bomet said they will prefer charges of murder and carrying excessive passengers on the driver who was among the injured.
Bomet Central subcounty police commander Musa Omari said investigations had begun. Once the driver who is admitted alongside passengers is discharged he will be arraigned, he said.
“For now he is still in hospital receiving treatment but once he is cleared we shall arraign him to answers to among other charges carrying excess passengers,” he said.
Omari said the driver, whose name was yet to be established, was admitted at the Longisa referral hospital but under the close watch of police officers.
The bodies of the deceased, he said, were moved to Longisa hospital morgue while the wreckage of the vehicle was towed to Bomet police station.
