In its latest annual report the company disclosed that the SEC served it with a subpoena last month requesting information and documents related to the project.

Peabody did not provide much detail in the annual report, saying only that it was cooperating and “believes that such other pending or threatened proceedings are likely to be resolved without a material adverse effect on its financial condition, results of operations or cash flows”

According to the Associated Press, Peabody spokesman Vic Svec said in an emailed statement on Tuesday that “we look forward to sharing information on what is a highly successful project”

The Prairie State energy campus in Illinois is the largest coal-fueled power plant built in the US in the last three decades.

It includes a 1600-megawatt electricity generating plant and an adjacent coal mine.

Its two electricity generators went online last year.

Peabody announced plans in 2007 to build Prairie State, and then later sold about 95% of its stake in the plant to eight power entities that represent 217 municipalities and 17 electric membership cooperatives in Illinois, Indiana, Kentucky, Michigan, Missouri, Ohio, Virginia and West Virginia.