The Maine Department of Environmental Protection has issued a Notice of Violation to Mallinckrodt, formerly known as the HoltraChem Manufacturing Company.

For several decades, the company manufactured caustic soda, chlorine bleach, hydrochloric acid and other chemicals at its now defunct plant in Orrington, resulting in what the DEP calls “significant mercury contamination to soils, groundwater and the nearby Penobscot River.”

The state’s Board of Environmental Protection ordered the site cleaned up more than 15 years ago for protection of public health and the environment. And the department has been overseeing the process ever since.

In a statement, the DEP said the company has failed to make meaningful progress for the past two years and expects that Mallinckrodt will “immediately resume efforts to remediate the site consistent with Maine law and the Department’s orders.”

The company did not immediately respond to a request for comment.

Three years ago Mallinckrodt reached a settlement in a decades-old lawsuit brought by the Natural Resources Defense Council and the Maine Peoples’ Alliance. As part of that settlement, the company agreed to pay at least $187 million to fund a remediation and restoration plan for the Penobscot River estuary and surrounding communities.