The City of Hattiesburg is suing Hercules Inc. and parent company Ashland Inc., claiming groundwater contamination from a closed factory may leach into the city's water supply.
The city filed suit Thursday in federal court in Hattiesburg.
Gary Rhodes, a spokesman for Ashland, says the company is reviewing the lawsuit and remains committed to a safe and effective cleanup of the former plant.
Ten residents and a church sued in October, alleging pollution in nearby neighborhoods. The company, the Mississippi Department of Environmental Quality and the U.S. Environmental Protection Agency have been testing for pollution at wells within a half-mile radius of the former chemical plant as well as onsite.
The suit states that the contamination continues to spread from the plant into the nearby air, groundwater and soil.