Police on Wednesday nabbed 40 illegal immigrants in Mana estate, Kayole.
Confirming the arrests, Njiru sub-county commander Patrick Mwamba said they received a tip-off from members of the public that there were suspicious men crammed in a small house.
The Ethiopian immigrants, aged between 10 and 25 years, could neither speak English nor Kiswahili but told police through a translator that they were headed for South Africa.
They told police that they arrived in the country on Monday, having paid an agent who was organizing the trip.
Police are looking for the agent as investigations continue.