HUNTINGTON BEACH, Calif.—The U.S. Coast Guard has designated the Mediterranean Shipping Company and others as parties of interest in an investigation into a vessel that was determined to be the source of an offshore pipeline leak in Southern California. Coast Guard and National Transportation Safety Board marine casualty investigators boarded a container ship, MSC DANIT, on Saturday in the Port of Long Beach that was involved in a January anchor-dragging incident discovered to be the source of the spill off Huntington Beach on Oct. 2, according to Lt. Cmdr. Braden Rostad. The designation announced in a statement on Saturday names ship operator Mediterranean Shipping Company S.A. and ship owner Dordellas Finance Corporation. It provides the owner and operator of MSC DANIT the opportunity to be represented by counsel, to examine and cross-examine witnesses, and to call witnesses relevant to the investigation, the statement said. An investigation into the spill, which …