New Zealand officials still have no idea how a large sum of drugs ended up on a Fonterra milk shipment to Algeria.
The drug haul is one of the biggest-ever intercepted in the North African country, an important market for the New Zealand dairy industry and worth $346 million.
In October 2012, Algerian police seized 165kg of cocaine, worth about $5 million on the dairy cooperative's container.
A report by New Zealand Customs says none of the parties involved had any success in gathering any relevant information about the incident.
Customs, Fonterra and the Mediterranean Shipping Company all experienced difficulties in gathering information from various contacts in Algeria, it said.
They also struggled to verify the integrity of the container seal on arrival in the country and the information obtained from other overseas sources.
Customs' trade manager Paul Campbell says all inquiries have been met with a minimal response from Algerian officials.
Mr Campbell said on Thursday he is confident that the drugs were not smuggled into the container in New Zealand, but would like to know how they found their way into it.
Customs is now looking at how it deals with future breaches at overseas ports, he said.