BILLINGS, Mont. (AP) — The owners of a Montana coal mine have asked a federal appellate court to intervene after a judge halted a planned expansion — a ruling the company says could shut down work and trigger layoffs.

Signal Peak Energy spokesman Mike Dawson said Friday that the company is appealing to the 9th U.S. Circuit Court of Appeals in hopes of avoiding any layoffs.

The 250-worker Bull Mountain mine north of Billings is one of the largest underground coal mines in the U.S.

U.S. District Judge Donald Molloy in August halted a planned expansion onto federal coal reserves. Environmental groups concerned over climate change impacts from burning the coal sued to block the expansion.

Signal Peak says the move could prompt 30 layoffs this month and another 50 layoffs by next March.