Maryland Occupational Safety and Health confirmed yesterday that it has issued citations against the operator of the Washington Metro system for four violations -- three of them classified as serious -- in connection with the deaths of two Metrorail workers.

The charges stem from an investigation of a fatal workplace accident that killed two employees in Rockville in January. MOSH, which conducted an investigation of the Washington Metropolitan Area Transit Authority along with the National Transportation Safety Board, found that WMATA had departed from its own workplace rules. The NTSB issued a scathing report earlier this week criticizing Metro for what it called the lack of a safety culture after a probe of last summer’s Red Line crash that killed nine.

In the Rockville incident, two veteran Metro employees who were working on the Red Line were killed when a truck-like vehicle used in track maintenance backed over them. MOSH recommended that WMTA improve its communications system so that uses dedicated frequencies and eliminates dead zones,