WARSAW: Polish pipeline operator PERN said on Friday it had neutralised over 30% of the contaminated Russian oil in its pipeline system and that it may take several months to completely clean the network.

Last month's discovery of an estimated 5 million tonnes of contaminated oil in Russia's Druzhba pipeline has halted flows to customers in Belarus, Ukraine, Poland, Germany and a number of central European countries.

PERN said that the contaminated oil is being blended with oil delivered by ship or from refineries' reserves.

Poland receives around 3 million tonnes of oil per month via the Druzhba, according to PERN.