Local police chief, Gen. Ahmad Ali Goudarzi, told state television on Tuesday that the opium had been concealed in a cement truck heading toward the capital Tehran.
Iranian authorities often confiscate large quantities of narcotics, but yesterday's seizure is the biggest in months.
Iran is the main route for drug smugglers to ship narcotics from the poppy fields of Afghanistan to Europe.
Authorities confiscate hundreds of tons of narcotics - mostly opium every year. In 2013, over 806 square miles of poppies were planted across Afghanistan, up 36 per cent from the year before.