The Customs Service says a large drug haul found in Algeria in a container of New Zealand milk powder could have been placed there anywhere along its transit.
Algerian police reportedly seized the Fonterra shipment after finding 165kg of cocaine or heroin worth about $5 million hidden inside.
The drug haul is reported as one of the biggest-ever intercepted in the North African country, an important market for the New Zealand dairy industry and worth $346 million.
Customs' trade and marine group manager Paul Campbell said on Wednesday the shipment passed through Port Otago and Port of Tauranga, then through Panama and Valencia in Spain where it sat on the docks for 24 days.
Mr Campbell said he is sure that the drugs were not hidden in the container while it was in New Zealand, but it could have been tampered with at any point on its several-month-long journey before being seized at Port Algiers.
He says Customs' attache in Brussels is collecting information and may soon travel to Algeria. Mr Campbell says he is not able yet to confirm the quantity or even the drug.
The Mediterranean Shipping Company on Wednesday confirmed that it carried the container but says it has to be careful what it discloses for legal reasons.
A Fonterra spokesperson says the dairy cooperative is part of Customs' secure export scheme and all its containers are packed at its own hubs, sealed, photographed and security tagged.