The Friday evening accident occurred at a location known for vehicle crashes near the Rift Valley town of Londiani, which is about 200 kilometres northwest of the capital, Nairobi.
Officers at the scene counted 51 bodies, but more people were believed to be trapped in the wreckage, Rift Valley police commander Tom Odera told The Associated Press.
The Kenya Red Cross Society said on Saturday 32 people were injured and hospitalized, and asked Kenyans to donate blood. It also said heavy rainfall interrupted rescue efforts and people were still trapped in wrecked vehicles.
Transport Minister Kipchumba Murkomen visited the scene on Saturday morning and said the government would relocate markets away from the highways to prevent such future accidents.
President William Ruto tweeted a condolence message to bereaved families describing the accident as “distressing” and urging motorists to be “extra cautious.”
Witnesses quoted by local media said the truck veered off the major highway and hit several vehicles before hitting pedestrians and traders. Witnesses shared photos of the vehicle wreckages mangled beyond recognition.
Police had said on Friday rescue operations would continue into the night.
The Kenyan Red Cross Society said they have set up stations at hospitals where people can report loved ones still missing and are providing psychological support to those affected.