A Wyoming-based coal producer, one of the largest in the United States, saw trading of its stock suspended by the New York Stock Exchange on Tuesday due to continued noncompliance with the exchange's listing standards.

Cloud Peak Energy, which last traded at 15.6 cents per share shortly before 9 a.m. MDT, did not immediately return a request for comment from K2 Radio News.

The company was warned in late December that it could be removed from the NYSE because their stock price had fallen below $1 per share for at least 30 consecutive days.

In its report to the U.S. Securities and Exchange Commission for the most recent fiscal year, the company concluded that "there is substantial doubt about our ability to continue as a going concern."

The company, in that filing, said it will continue to evaluate restructuring options and review its capital structure.