One person was arrested on Monday for illegal possession of ballot materials in Obungu area, Kisumu county.
Police also seized a vehicle carrying empty ballot boxes.
Some of the boxes were labelled with the names of different polling stations including Kanyamedha, Okore and Ogonda.
The suspect is believed to have wanted to use the materials to rig party nominations.
ODM primaries in Kisumu are set to begin on Tuesday.
County commander Titus Yoma said they are investigating to establish where the boxes were being taken to.
