More than 50 Ethiopian immigrants were on Friday arrested at Baba Dogo and Huruma estates, Nairobi.
Detectives from the Transnational Organised Crime Unit suspect that the immigrants were being trafficked to South Africa through Tanzania.
The aliens were found in separate residential homes in the two estates.
Omar Adan who was accused of harbouring the immigrants has also been arrested.
Police are still trying to track down the key suspect in the human trafficking ring.