19 C.F.R. § 19.34
Port directors shall exercise such supervision and control over the transactions covered by §§ 19.29 through 19.32 as will insure that there will be no unauthorized access to the imported wheat and no unauthorized mixing, blending, or commingling of such imported wheat. Importers, exporters, proprietors of Customs bonded warehouses, bonded common carriers, and others handling imported wheat in continuous Customs custody shall maintain such records as will enable Customs officers to verify the handling to which the imported wheat has been subjected, and to establish whether there has been a proper accounting to Customs for any increase in the quantity of the wheat or shortages resulting from shrinkage or other factors. These records shall be retained for a period of 5 years from the date of the transaction. Port directors shall from time to time request the appropriate Customs officer to examine such records of importers, exporters, warehouse proprietors, bonded common carriers, and others handling such wheat in continuous Customs custody as may be deemed necessary to ascertain whether there has been any failure to comply with the applicable Customs laws and regulations.
19 C.F.R. §19.34