US-based Massey Energy, owner of the West Virginia mine where 29 people died in April, said increased federal inspections have curbed productivity during the second quarter of 2010.
The company's coal output for the quarter was 500,000t lower than expected due to reduced productivity amid distractions from the Upper Big Branch explosions, temporary shutdowns and increased inspections.
Massey said its shipments during Q2 2010 dropped below its projections by about one million tons due to lower productivity and temporary shutdowns.
The company posted a net loss of $55.1m for the first half the year.
Massey CEO Don Blankership said he may seek to access other sections of the reserves at the mine that were not affected by the explosion.