MORGANTOWN, W.Va. — A federal report released today claims federal inspectors either missed problems at West Virginia’s Upper Big Branch mine or failed to inspect the areas where they existed in the 18 months before a deadly 2010 explosion.

However, an internal review concludes there’s no evidence those failures caused the disaster.

The Mine Safety and Health Administration posted the report online today after a private briefing with relatives of the 29 miners killed in the nation’s worst coal mining disaster in four decades.

The report acknowledges multiple failures by field staff in MSHA’s largest region, southern West Virginia’s District 4. It also said their effectiveness was compromised by internal communication problems and by federal budget cuts that had created staffing shortages, inexperience and a lack of sufficient training and managerial oversight.