Municipal Council worker Sajan and two other sweepers were cleaning the drain in Sunder Nagar when the cartridges and magazines were found, police said.
A case under Arms Act had been registered against unidentified persons, police said.
Police said that SLR was apparently of some police and para military personnel. A wireless message has been sent to all police stations and headquarters of paramilitary forces like BSF, CRPF, ITBP and CISF.