The recovery was made last night after villagers who were crossing the drain in Kamalganj police station area found the cartridges and informed the police.
A police team which rushed to the area recovered 2,000 empty cartridges from the drain and some 3,000 others from secluded spots nearby, police said today, adding two people have been taken into custody for questioning.
Police is also looking for a dismissed constable Asgar Ali who was found involved in a scam of cartridges at Shahjahanpur police lines in the past.
He said Ali is contesting the election to the post of Pradhan from nearby Katrauli Patti village but is missing since the recovery of empty cartridges.
A hunt has been launched for Ali, the SP said.