OLYMPIA, Wash. -

Authorities have cleared a camp that had been set up on railroad tracks by protesters opposed to hydraulic fracking.

Olympia Police Chief Ronnie Roberts says officers arrested a dozen people Friday morning. No injuries were reported.

The Olympian newspaper reports that with the camp cleared, a train carrying ceramic proppants, or fracking sand, was able to pass.

Police in riot gear kept people away from the tracks as the train passed through the city.

Protesters had been blocked the tracks since Nov. 11 to prevent the train from leaving the Port of Olympia. Activists with the group Olympia Stand say they're opposed to fracking, a technique used by the energy industry to extract oil and gas from rock.

The Port of Olympia handles cargo called ceramic proppants, or fracking sand, used in that extraction process.