Work’s begun to clean up a chemical spill that briefly threatened the Missouri River over the weekend. 150,000 gallons of potentially hazardous liquid leaked from the site of a former tannery at Salix near Sioux City.

Officials from the U.S. Environmental Protection Agency came to inspect the scene, and Kevin Baskins with the Iowa Department of Natural Resources says they began pumping out the liquid last night. It had been contained in an oxbow, a small lake that’s in a former river bend cut off from the Missouri.

Baskins says they’re pumping some of the contaminated fluid into tankers, and doing some sampling to determine just what’s in the fluid and how it can properly be handled. One chemical reportedly confirmed by initial tests on the mix is chromium, a chemical often used in tanning leather.

Officials believe the leak originated with a ruptured pipe connected to a wastewater lagoon at the former Superfund site near Salix, Iowa. The wastewater will be taken to a treatment facility before being discharged.