Described by CBSA as "a significant seizure," the find was the result of an inspection on April 13.
CBSA officers conducting courier examinations inspected a shipment declared as shoes. Officers emptied the contents of one cardboard box that felt unusually heavy and had an "earthy" smell to it, according to CBSA.
Officers then discovered the suspected opium, concealed within the cardboard piles of the box.
The suspected opium was turned over to York Regional Police. One suspect has been arrested in connection with the crime.
The CBSA processed over 3.7 million courier releases at Hamilton International Airport in 2014, according to the agency.
In 2014, the CBSA in the Greater Toronto Area made 123 opium seizures totaling over 139 kilograms.
Those with information about suspicious cross-border activity is asked to contact CBSA Border Watch at 1-888-502-9060.