(CNN) The National Park Service has closed several portions of Indiana Dunes National Park after a chemical spill killed hundreds of fish in the area, according to a statement by Portage, Indiana, a nearby city.

The spill occurred last week at the east branch of the Little Calumet River, about three miles upstream from Lake Michigan, Indiana Dunes National Park confirmed in a statement. The National Park Service has closed the Portage Lakefront, the Riverwalk beach area and waters out to 300 feet.

The company responsible is ArcelorMittal, a steel and mining company headquartered in Luxembourg. In a statement released Friday, the company said the incident was due to a failure in a blast furnace water recirculation system at its steelmaking plant in nearby Burns Harbor.

The accident released wastewater containing high levels of ammonia and cyanide into the river. The company called it an isolated event.

"ArcelorMittal apologizes and accepts responsibility for the incident from the Burns Harbor facility. We are working closely with state and federal regulatory agencies to address the situation and to prevent its reoccurrence," the statement read

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