In a pre-dawn swoop on a few rice go-downs and mills, city police arrested 16 persons belonging to two gangs, which were involved in smuggling Re.1 per kg ration rice in large quantities to Karnataka and also seized 15000 kg rice and machineries, a lorry, an Indica car and 4 motor bikes, here on Tuesday. Killing of 2 youths, both belonging to rival groups engaged in rice smuggling, had prompted the police to undertake the raids, said a senior police official.