KeNHA said the decision to close the section was necessary to allow emergency responders to manage the situation and restore normal traffic movement.
The agency did not immediately provide details on the number of vehicles involved or whether there were any injuries resulting from the crash.
Motorists using the route have been cautioned to expect delays and are advised to plan their journeys accordingly.
The authority urged drivers to consider alternative routes where possible to ease congestion along the affected stretch.
At the same time, a multi-agency team comprising traffic police, emergency services, and road maintenance personnel has been deployed to the scene.
The team is working to clear the wreckage, assess any damage to the road infrastructure, and ensure that the area is safe before reopening it to traffic.
“The Kenya National Highways Authority (KeNHA) wishes to notify motorists that the Nairobi Southern Bypass (Ole Sereni-bound), between Thogoto and Dagoretti Interchanges near Karinde, has been temporarily closed following a road traffic accident earlier this morning,” read part of the notice.
The Nairobi Southern Bypass is a key transport corridor that connects major highways around the capital, helping to ease congestion within the city centre.
Any disruption along the route often leads to traffic build-up on alternative roads, especially during peak hours.
Drivers have been urged to exercise patience and cooperate with traffic officers managing the situation.
KeNHA also reminded motorists to observe road safety rules, including maintaining safe distances and adhering to speed limits, particularly in areas where emergency operations are underway.