One of the sources said that Hungary plans to store the oil received this month but not to process it.
Hungarian energy company MOL and Russian pipeline monopoly Transneft did not reply to requests for a comment.
Russia halted oil flows along the pipeline to Eastern Europe and Germany in April because of contaminated crude, leaving refiners in Europe scrambling to find supplies.
This week, MOL said it would start taking clean Russian oil later this week via Druzhba after agreeing to store 100,000 tonnes of contaminated crude.