The company blamed operational problems caused by the harsh winter weather for the decline.

Production from its Stockton mine near Hazleton, Pennsylvania, fell 9.1% from the previous three-month period.

The anthracite coal mining company's run-of-mine production was 85,270t for Q1 2014, down 18.3% from Q4 2013.

Sales for Q1 2014 totalled 36,449t, down 31.6% from the year before and 13.8% from Q4 2013.

Its clean coal stockpile stood at 2,702t at the end of Q1, just below the 2,922t at the end of Q4 2013.

Atlantic Coal managing director Steve Best attributed the production and sales decline to "the coldest and longest winter in Pennsylvania for 20 years”

He said that washing coal at freezing temperatures had been particularly problematic, with mining operations often suspended or scaled back.