Roberts said in a one week period four miners, including two UMWA members, were killed. Since the start of the year there have been 14 fatalities in American mines.
He called on the MSHA to fully investigate each incident and issue harsher penalties where justified.
Earlier during June 200 UMWA miners from every Alabama coal mine where the union represents workers protested outside a Holmes Safety Association dinner. Roberts said the miners voiced their anger about lax compliance by state mine operators and lax enforcement by MSHA.
