Hundreds of residents of Mukuru and Kibera slums were left homeless on Tuesday and Wednesday after fire gutted down their houses.
Police say several people were injured in the Mukuru slum fire on Wednesday night.
The cause of the fire was not immediately clear but it started in one structure and spread to the others.
In Kibera, a number of tenants were injured while trying to put out the fire before fire fighters arrived.
Several houses were razed in the fire on Wednesday morning.
The fire is said to have spread quickly from one of the structures.
Police have launched investigations while those affected have asked for help to reconstruct the structures.