(Tualatin, OR)  --  The Occupational Safety and Health Administration, or OSHA, is looking into the subcontractor who caused Wednesday's gas explosion.  KATU-TV reports that the subcontractor has been cited by OSHA six times over the last five years, with some violations considered serious.  The Loy Clark Pipeline Company, out of Tualatin, said yesterday that all proper protocols were followed prior to digging.  Eight people were injured in two simultaneous explosions after the subcontractor struck a gas pipeline at a building in the Northwest 23rd Street shopping district.