CHARLESTON, W.Va. -- Federal regulators issued more than 300 more violations last month during inspection sweeps of the nation's underground coal mines, as the Obama administration continued what it said is stepped-up enforcement following the April deaths of 29 miners in an explosion at Massey Energy's Upper Big Branch Mine.U.S. Mine Safety and Health Administration inspectors issued 326 citations and orders at 15 mines in West Virginia and eight other states, with nearly half of those being classified as serious violations.MSHA also took 232 enforcement actions at 15 metal and nonmetal mines, mostly in Western states including California and Nevada."We are continuing to find serious threats to miners' safety and health," said Joe Main, assistant labor secretary for MSHA. "While some operators are finally getting the message, others are not."In a news release, MSHA noted Massey subsidiary Elk Run Coal Co.'s Seng Creek Powellton Mine, where agency inspectors in late September issued 11 closure orders alleging ventilation violations the agency said could lead to mine explosions and black lung disease.Main, a former United Mine Workers safety director, launched what MSHA calls "impact inspections" after Upper Big Branch, to target mining operations with a poor compliance history, high number of accidents, and previous violations related to poor ventilation or faulty roof conditions.Impact inspections in September also produced 60 citations and enforcement orders at three other Massey operations, the Triumph and Freedom Energy mines in Kentucky and the Marsh Fork Mine in West Virginia.Less than a half-hour after MSHA's Tuesday announcement, Massey said it plans to shut down all of its underground mines for the day on Oct. 29 for a day of training and to "reinforce the fact that safety is more important than production.""Despite considerable training, there have been recent instances where our miners were not doing the right thing as they had been trained to do," said Massey CEO Don Blankenship. "The idling of production reinforces our philosophy that safety is first and production is second."After MSHA's inspection at the Seng Creek Mine, Massey said it had fired a foreman and two hourly workers and suspended nine miners for three days. The company called the situation at the mine "very frustrating and totally unacceptable."And last week, Massey alerted shareholders that its Cloverlick Coal Co., in Harlan County, Ky., had received an imminent-danger order from MSHA after a construction contractor was caught standing on the edge of the slanted metal roof of a shop building in a body hardness that was not tied off.Nonunion Massey is not the only company being hit with repeated citations in MSHA's impact inspections.Patriot Coal Co.'s Federal No. 2 Mine, a unionized operation in Monongalia County, has been targeted in three rounds of inspection sweeps since April. The mine's total number of violations has increased, as has the share of the violations deemed significant by agency inspectors.Federal No. 2 is also under federal criminal investigation because of allegations of falsified safety examinations at the mine, but MSHA did not mention that operation in its news release about the agency inspection sweep.Reach Ken Ward Jr. at email@example.com or 304-348-1702.