MINSK: Belarus's Naftan refinery has started loading clean Russian oil after a major oil contamination earlier this year, the Polotsktransneft Druzhba pipeline operator said on Thursday.The operator said in a statement it had started cleaning part of the Druzhba pipeline between Unecha and Polotsk and that it had pumped dirty oil back to Russia from the Unecha-Polotsk-1 section of the pipeline.