The fire at a chemical plant in Pennsylvania on June 8 was likely caused by an electrical circuit malfunction, rather than by arson or any product or manufacturing process, Miller Chemical said.
The company's fertilizer manufacturing facility in Conewago Township, Adams County, was destroyed in the blaze.
Firefighters used large amounts of water and some foam to extinguish the fire, which burned for more than 12 hours. Some of that water overflowed from a runoff retention pond and entered Conewago Creek.
According to the Pennsylvania Department of Environmental Protection (DEP), runoff from the Miller site reduced the concentration of oxygen and increased the presence of nitrogen compounds in the creek, killing a large number of fish. However, public drinking water supplies in the area were not contaminated.
The DEP is conducting tests in the Conewago Creek to monitor contaminants and see how quickly they dissipate. Oxygen levels have improved, officials said.
For the time being, the New Oxford Municipal Authority's water intake located on the Conewago Creek remains closed and the water company is receiving alternative supplies through an interconnection with the York Water Company and other sources.
Mandatory water use restrictions are still in effect, requiring customers of the New Oxford system to conserve as much water as possible.
Miller has been working with environmental experts and a state-certified remediation firm on-site to prevent further runoff into local waterways.
The company has also erected a large above-ground tank that will be used to contain water pumped from the affected area before its removal.