All the company's containers left New Zealand with sealed lids, he said.
"We're aware of reports from Algeria that a container loaded with milk powder is being investigated. We're waiting to hear which Algerian authority is leading the investigation and we're on standby to provide any information as required,'' said the spokesman.
Customs was aware that the cargo in which the drugs was found was unloaded and reloaded in Panama and Valencia, Spain, Mr Campbell said.
"We have engaged our attache in Brussels and he will be working to establish the facts.
"Customs has very high confidence in the integrity of New Zealand exports.''
The Agence France-Presse news agency reported that the container had been imported by Algerian company ONIL.
The haul was thought to be one of the largest ever intercepted in the North African country.
A New Zealand Police spokesman said it would get involved only if there was a suggestion of unlawful activity in New Zealand.