Unused and decaying materials at the Decorative Panels International plant in Alpena, a portion of which were sent to the plant’s wastewater treatment process but could not be treated, are to blame for the odor, the city said. DPI officials are currently removing the products, which could cause more odor, but the process should be complete in the next two days.

State environmental officials have confirmed the odor is not from the city’s wastewater treatment plant, the news release said.