Published: Oct 19, 2010 5:07 PM EDT
Updated: Oct 19, 2010 2:07 PM EDT

CHARLESTON, W.Va. (AP) - Federal regulators say they're still uncovering hundreds of serious violations at mines in more than a dozen states.

The Mine Safety and Health Administration says inspectors issued nearly 600 citations at 30 problem mines in September. MSHA director Joe Main says the numbers released Tuesday show some mine operators are not getting the message about safety.

MSHA began inspection blitzes after 29 miners died in an explosion at Massey Energy Co.'s Upper Big Branch mine about 50 miles south of Charleston. The April 5 explosion was the deadliest at a U.S. coal mine since 1970 and remains the subject of criminal and civil investigations.

MSHA says four of the 15 coal mines targeted during the blitz are owned by Massey in West Virginia and Kentucky.