The oil spill was caused by a rupture in the Nizhnevartovsk-Kurgan-Kuibyshev pipeline on March 8, some 150 kilometers west of the regional capital, Ufa. Officials say they expect the cleanup to continue at least until early next week. Initially, they said it would be completed by March 11.
A spokesman for the republic's Ministry of Natural Resources says analysis shows the concentration of chemicals in one nearby river is 26 times higher than the norm. Chemicals have also been detected in a second river that supplies the town of Tuymazy with drinking water.
Officials say that, for now, there is no danger of Tuymazy's water supply being contaminated.