A highly toxic and possibly illegally traded chemical substance was the main culprit in the crisis with contaminated oil, which had Russia interrupt oil flows on its Druzhba pipeline to Europe for around two months this spring, Reuters reported on Wednesday, quoting the results of three different tests. At the end of April, Russia halted supplies via the Druzhba oil pipeline to several European countries due to a contamination issue, which the Russians said was deliberate.

Russia said at the time that the oil was contaminated with organic chlorine, a substance used in oil production to boost output but dangerous in high amounts for refining equipment. The amounts of the chemical were found to be at levels much higher than the maximum allowable amount.  A month after the crisis started, supplies were not restored and analysts and traders were saying the progress in restarting oil flows was very slow while costs could be very high, despite Russia’s assurances that clean oil would resume flowing through the pipeline westward to Europe in the second half of May.