According to the Namibian Broadcasting Corporation, the drugs were allegedly hidden in boxes marked as printing papers.
The container is believed to have originated from Brazil and was en route to South Africa or Angola.
It is said the container was offloaded a few days ago at the harbour and customs officials acted after a tip off.
One suspect was arrested and the police in the Erongo region expect to make more arrests, according to the broadcaster.
AT/jn/APA