SALEM, Ore. (AP) — Officials in Portland, Oregon, are cleaning up tear gas residue from the streets, dirt and possibly the storm drains after the chemical was used repeatedly by both police and federal officers during protests over racial injustice.

The Portland Bureau of Environmental Services cleaned and took samples from six storm drains last week around the federal courthouse and a building with a police station and jail that have been targeted in nightly demonstrations.

Environmental officials aimed to prevent pollutants from reaching the Willamette River that runs through downtown and determine the possible impact if contaminants did flow into the waterway.

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