Traffic was disrupted along the Mai Mahiu-Limuru road after a truck rammed into eight vehicles.
The Thursday accident left scores with injuries as residents hurried to help rescue those trapped in vehicles.
The truck was driving downhill before it developed mechanical problems and rammed into the oncoming cars, according to witnesses.
It crashed by the roadside and left scores of motorists trapped inside the wreck.
Traffic police have advised motorists to seek alternative routes as they move in to clear the section of the road.
Road accidents Kenya
A 2019 report by the National Transport and Safety Authority revealed a rise in the number of fatalities linked to road accidents this year compared to 2018.
The report indicated that more men die in road accidents compared to women.
1756 men perished in road accidents compared to 386 women from January 16, 2018, to September of the same year.
Nearly every hour, a man dies in a road accident in Kenya, as per the report.