A police official, who asked for anonymity because he is not authorised to speak to the press, said on Saturday that three suspects dropped a bag and ran after police confronted them near a highly populated slum.
The official says police found 6kg of ammonium nitrate and other items they believe can be used to make a bomb.
Police said an improvised bomb killed 1 person and injured 32 others in downtown Nairobi last month. Officials believe ammonium nitrate was used to assemble that bomb.
Al-Qaeda linked al-Shabaab militants from Somalia have threatened to retaliate after Kenya sent troops to Somalia to pursue the militants.- SAPA