Two people died and 39 others were injured in two separate accidents that occurred on the Mai Mahiu-Narok road at the weekend.
The injured were taken to Naivasha sub-county hospital; so far 14 have been discharged while the others are still undergoing treatment.
The first incident involving two vehicles took place at Suswa junction on Friday night.
"The driver of the Mitsubishi vehicle was driving towards Nairobi and attempted to overtake a fleet of vehicles but collided with an oncoming matatu," Naivasha OCPD Titus Mathuku said.
Eight people were injured and were first taken to Kijabe Mission Hospital before being referred to Naivasha hospital.
The second happened on Sunday morning at Satellite.
"The bus driver rammed on the rear of the stationary [trailer-truck] and died on the spot together with a female passenger in the front seat," the OCPD said.
Twenty-nine passengers in the bus sustained serious injuries.
Mr Mathuku said the lorry driver, who was sleeping inside the vehicle, escaped.
"We are looking for him to explain what transpired before the morning accident."
The wreckages were towed to Mai Mahiu police station.
The medical superintendent, Dr Joseph Mburu said two victims have lost their limbs and two others sustained serious head injuries.
"The four are under close observation after sustaining life threatening injuries but the other 11 are in the general ward," Dr Mburu said.