In July 2012, 255 workers were let go and a further 138 workers followed in December but 50 of them were later re-employed.
As a result of these cuts, the Pennsylvanian company has almost halved its workforce in the last year.
PBS general counsel Lori J Mason said the lay-offs were permanent and were made across the board, including administration and management.
"We are not idling or closing any minesites," Mason told WJAC TV.
“We are just reducing our production and along with that we needed to reduce overhead.”
Mason blamed the weak economy, escalating costs and an overall decreased demand for the continued lay-offs.
"Right now, the 2013 coal market isn't getting better but we hope that it's hit the bottom," she said.
PBS Coals has five surface mines, five underground mines and two coal preparation plants.
Mason said the cuts were made across the sites.