Theft cause of oil spill near Samara?
The leak spread over an area of almost 4,000 square metres. A channel, which is no longer part of the Samara river, is among the worst affected areas with a 20-centimetre-thick layer of oil on the water.
It's thought someone illegally cutting into the pipeline to steal oil may have been the cause of the spillage.
An investigation is under way as environmentalists attempt to repair the damage.