In early August, a coal mine in Pennsylvania exploded in flames, killing three workers.
It was the second such incident in the state in less than two years.
The cause of the explosion, officials say, is likely caused by a failure of safety systems at the mine.
That was the first known coal-related accident at the site.
The fire spread quickly through the mine, destroying the mine’s power generator, a gas-fired boiler and a large water pump.
The mine’s owner, Enbridge, has agreed to pay $400 million in compensation to the families of the miners.
But environmental groups and some state officials say the mine is far from clean.
“Enbridge and other companies that operate coal-fired power plants have long used dangerous, toxic chemicals that can kill people,” said Brian Shrum, executive director of the Environmental Working Group, which advocates for a cleaner-burning energy system.
“That’s what we are seeing at the Enbridge mine in this incident.
The coal company must do a better job in its coal-burning infrastructure.”
Enbridge’s decision to pay compensation for the miners’ families will also add to a $50 billion liability that has been building at the company.
But Enbridge says it is also paying to clean up its mine, and it is committed to reducing the pollution from its plants.
“We have taken significant steps to improve our coal-mining operations, including developing the most comprehensive and efficient management and control system in the industry,” the company said in a statement.
The company also said it is “committed to improving safety and environmental performance.”
The Enbridge disaster is just one example of a broader problem with coal-powered power plants in the United States.
The Environmental Protection Agency has found that nearly a third of the country’s coal-power plants are failing to meet safety standards.
In many cases, regulators say, the companies that own the plants are not required to maintain and improve them.
In May, the EPA ordered four coal-mine operators to improve their systems and conduct safety audits of their operations.
The agency also fined a coal company $20 million for failing to maintain safety and air quality at a coal-burner in Wisconsin.