Two decomposing bodies of unknown male persons were found in Ngong River.
The bodies were discovered along the Mukuru slums on Wednesday.
Residents told police they had spotted the bodies at Gatope area in the slum.
Police suspect the bodies were thrown at an unknown place and were swept downstream.
The bodies seemed to have been in the water for more than two days.
Nairobi county fire brigade team was called in and managed to retrieve the bodies.
The scene was documented by police and bodies moved to the mortuary.
Nairobi police boss Adamson Bungei said they are yet to identify the victims.
He said a team of experts is investigating the incident and appealed to anyone whose relative or friends are missing to visit City Mortuary to help with investigations.
Cases of discovery of bodies are common. Some drown, others are victims of hit and run while others are killed after being targeted.
Most of the cases are pending under investigation.
