Shipments of tin concentrates from DR Congo have been restricted in recent weeks as local traders have refused to pay higher taxes, according to Bloomberg News.

Congo’s customs and excise office, or Ofida, are taxing nearly 11 percent on $14 per kilogram of tin ore, up from $4 per kilogram, said John Kanyoni, president of the Association of Exporters of Minerals in North Kivu. Talks between traders, government, and tax authorities to resolve the issue are underway, he added. Exports started slowing three weeks ago and it will take at least another month to implement a solution, said Gilbert Samine, provincial director of the Centre for Expertise, Evaluation and Certification, a government body which monitors exports.

ITRI estimates that DR Congo produced some 13,000 tonnes of tin-in-concentrate last year, or 4% of world production.