The truck exploded after it had crashed into several vehicles north of the central town of Naivasha, an official with the National Disaster Management Authority told Reuters.
"More bodies are still trapped inside the burned vehicles," Red Cross volunteer Moha Maris told Reuters.
Fuel tanker loses control, runs into 5 vehicles & bursts into flames along Nakuru Nairobi highway.Naivasha fire brigade & #RedCross at scene— Kenya Red Cross (@KenyaRedCross) December 10, 2016
Earlier reports said that the truck was carrying highly inflammable chemicals.
The incident took place 80 km from Kenya's capital, Nairobi.