PORTAGE, Ind. (WLS) -- The Indiana Dunes National Park has reopened a beach area that was closed after state officials discovered a steel plant leaked toxic levels of cyanide and ammonia-nitrogen into a Lake Michigan tributary, killing several thousand fish.
The park announced that the Portage Lakefront and Riverwalk's beach was open to the public on Thursday afternoon. It comes nearly a week after the Indiana Department of Environmental Management alleged Portage steel factory owner ArcelorMittal dumped toxins into the Little Calumet River.
State officials estimate that nearly 3,000 fish were killed in the spill.
RELATED: 3,000 fish killed in Little Calumet River by cyanide leak at Indiana steel factory: state officials
Indiana Dunes National Park officials said U.S. Steel identified a second smaller oil spill nearby after the cyanide leak. U.S. Steel quickly cleaned the affected area, the park said.
Water tests in Indiana show that cyanide concentrations have fallen to acceptable levels.
RELATED: Indiana Dunes beach closed after steel plant releases cyanide in Little Calumet River
ArcelorMittal and the Indiana Department of Environmental Management have been criticized for failing to report the cyanide leak until several days after the water of the Little Calumet River was poisoned.
According to the Indiana Department of Environmental Management, ArcelorMittal exceeded the daily maximum total for cyanide and ammonia nitrogen release. The department, which is leading the investigation, has requested ArcelorMittal help clean up the spill and monitor the river's chemical concentration.
The steel factory admitted to leaking the chemicals last week, and blamed the exposure at its Burns Harbor facility to a "failure at the blast furnace water recirculation system," an ArcelorMittal spokesperson said.
Although the state's Department of Environmental Management responded as early as Aug. 12 to a report of "distressed fish" in the east branch of the river, the public was not notified of a chemical leak until Aug. 15, Portage Mayor John Cannon said in a statement. Cannon blamed the steel factory and state officials for withholding details about the leak.
"IDEM needs to be held accountable to let our residents and our visitors know what's going on," Portage Mayor John Cannon said. "This is the middle of summer. This is the height, the peak of fishing season."
The National Park Service closed the water out to 300 feet at the Portage Lakefront and Riverwalk beach area last week. The trails remained open.
The National Park Service, as well as local and state officials, will continue to monitor the Indiana Dunes.
Indiana Dunes National Park reopens beach after steel plant leaks cyanide into Little Calumet River