A Nyamira Express coach has been captured smouldering with smoke coming out of it along Forest Road.
The bus is seen in a video shared online by a social media user burning.
It was not immediately clear whether the ill-fated bus was on its way to Nyamira or had just arrived in the capital Nairobi from Nyamira.
Also not clear is what was behind the burning.
Nyamira Express buses ply the Nairobi-Nyamira route, ferrying passengers to the rural areas of the greater Nyanza region.
The buses are popular with those hailing from the Nyanza region because they are cheap. They usually pick passengers at the famous Machakos Country Bus station in Nairobi.
This is not the first time that a Nyamira Express bus has been involved in an incident. Some of the buses in the fleet have been involved in grisly traffic incidences.
In 2016, a Nyamira Express bus was involved in an accident that left 22 people injured.
Last year, the company procured a number of brand new Isuzu buses in a bid to boost consumer confidence.
Nyamira Express buses are said to be under the same management as the Guardian buses that ply the same route.
While it caters for low-income customers, Guardian buses cater for the high-income customers.