The customs officers at Washington, DC, Brownsville, Tex., Hoboken, N.J., Honolulu, Hawaii, Jamaica, L.I., N.Y., Laredo, Tex., Miami, Fla., New Orleans, La., San Francisco, Calif., San Juan, P.R., San Pedro, Calif., or Seattle, Wash., shall keep a record of such packages as may be delivered to representatives of the Department of Agriculture, and upon the return thereof shall prepare a mail entry to accompany the dutiable package and deliver it to the postmaster for delivery or onward dispatch or in appropriate cases subject the shipment to formal customs entry procedure.