The four were travelling in a matatu from Ongata Rongai to Kiserian at 10pm on Sunday night when the incident occurred.
Two bodies were retrieved on Monday morning from Kandisi River, while another was sighted in the afternoon according to Kenya Red Cross Communications Manager Nelly Muluka.
Muluka said that it was not clear how many people were in the matatu at the time of the incident and if any survived.
She said: “A body was sighted this afternoon (Monday) and efforts are on going to retrieve the body before it is dark. We are as yet unable to ascertain how many people were in the vehicle.”
The badly damaged matatu was recovered downstream Kandisi River.
In a separate incident two other people drowned in separate incidents in Magadi on Sunday night, according to area administrators.
Kajiado North DC Mwangi Kahiro confirmed that the body of a man was recovered from Entasopia River in Magadi after he was swept away as he tried to cross the surging river.
Kihiro says that the body of another man was recovered in a ditch along Kangawa Road.
Two other vehicles were swept by Lemelepo River in the area but the occupants escaped unhurt, 2 swimming to safety and six others were rescued by locals.
Kenya Red Cross said on Saturday that it had put all its 64 countrywide branches on alert following the onset of the rainy season.
In Nyanza, 200 households were reported to have been marooned by the floods in Kisumu and Nyando districts following the ongoing heavy rains that have also been experienced in parts of Western Kenya.
Kenya Red Cross regional coordinator Emmanuel Owako reported that they had dispatched a team of volunteers and Red Cross officials to the ground to respond to the distress calls of an estimated 1500 people.
Speaking to Capital FM News, Owako says most of the families are still stuck in their houses that are already submerged in water in Nyamasaria and Orongo within Kisumu and other areas in Nyando.
“We are advising those who are in low lying areas to move to higher grounds when it still early. In Gem we have already advised about 375 people to relocate to St Alloyce Primary School,” he said.
He says the team will assist in rescuing those trapped and giving immediate assistance to the affected families.
Owako in the meantime is appealing to families living in flood prone areas to move to higher grounds as a precaution measure to prevent loss of lives and property.
He says rains are still moderate but there are signs of floods as the intensity of the rain continues to grow.
Motorists approaching Kisumu from Ahero have also been advised to be cautious while approaching the over flooded Nyando bridge.