CHARLESTON, W.Va. -- In the months before the deadly explosion at Massey Energy's Upper Big Branch Mine, company officials were engaged in major disputes with state and federal regulators over serious ventilation problems at the sprawling underground mine in Raleigh County.Regulators had cited Massey's Performance Coal subsidiary in December for ignoring orders that it redirect potentially dirty air from a conveyor belt tunnel away from the longwall machine section where miners were working.And last month, inspectors from the state Office of Miners Health, Safety and Training recommended the violation for "special assessment" -- which carries heavier fines -- after Massey delayed in fixing the problem.Also last month, federal inspectors cited Massey when they found airflow was half of what was needed to clean mine air and control levels of explosive methane underground.That violation prompted one of more than 60 orders issued in the last 15 months in which U.S. Mine Safety and Health Administration officials ordered miners withdrawn from parts of the Upper Big Branch Mine.The dispute over ventilation of the mine, detailed in documents MSHA posted on its Web site Friday afternoon and in state records obtained under the Freedom of Information Act, adds to increasing evidence of growing safety problems at the mine before Monday's deadly blast."The more I learn about the extent of these violations by Massey at the Upper Big Branch Mine alone, the angrier I get," said Sen. Robert C. Byrd, D-W.Va."To me, one thing is clear -- for a company that has had this number of violations at just one coal mine -- one must seriously begin to question the practice and procedures of this particular coal company, and it needs the most serious scrutiny from Congress and the federal regulators," Byrd said in a prepared statement.Massey CEO Don Blankenship continued to defend his company's safety record, issuing a letter to shareholders insisting that media reports suggesting the explosion "was the result of a willful disregard for safety regulations are completely unfounded."Among other things, Blankenship said that most of the citations issued by MSHA to the Upper Big Branch Mine "were resolved on the same day they were issued."But the latest documents released by MSHA included one withdrawal order that was issued after inspectors on Jan. 11 found large accumulations of explosive coal dust on conveyor belt rollers. Coal dust that builds up on and around belts can ignite from friction, and such problems were among the central causes of the January 2009 Aracoma Alma No. 1 fire that killed two Massey miners.At Upper Big Branch, inspectors wrote that a mine foreman found the problem two days earlier, on Jan. 9 and that the company had "been working on it.""At the time of this inspection, no one was working on it," the MSHA inspectors wrote. "The operator engaged in aggravated conduct by his failure to correct the known hazard before running the belt."MSHA issued another withdrawal order on March 15 after an inspector found that accumulations of coal and coal dust had been allowed to build up behind the longwall conveyor belt drive. Nine days later, on March 24, an MSHA inspector reported that "no apparent effort was made by the operator to remove accumulations" cited in the previous violation.Also back in January, state inspectors cited Massey in a running ventilation dispute when they found the company had made major changes to the Upper Big Branch Mine's ventilation system without first seeking and receiving agency approval.The change was made in mid-December, when Massey directed air from a working mining section into the longwall belt tunnel. Such changes need state approval, and state inspectors were concerned Massey's airflow plan would result in potentially dirty air going from the longwall belt tunnel into areas of the section where miners were working. State inspectors cited Massey on Dec. 31, 2009.Four days later, Massey sought approval to change the airflow so that the potentially dirty air would not end up in the longwall belt tunnel.State officials approved that proposal the same day, Jan. 4. But during a mine visit on Jan. 27, inspectors found that the old configuration -- which the state had rejected -- was still in use. Inspectors did not mark the problem as being corrected until early March.Reach Ken Ward Jr. at email@example.com or 304-348-1702.