Preliminary data released by the U.S. Department of Labor’s Mine Safety and Health Administration (MSHA) indicate that 28 miners died in 2015 in work-related accidents at the nation’s mines, down from 45 in 2014. The figure represents the lowest number of mining deaths ever recorded and the first year that mining deaths dropped below 30.

“While coal mine closures had some effect on the historic low number of mining deaths, actions by MSHA and the mining industry to improve mine safety have been a major factor,” said Joseph A. Main, assistant secretary of labor for mine safety and health.

Read the full MSHA press release here.