A 37-year-old Port Huron man and 31-year-old Port Huron woman were arrested during the narcotic investigation that occurred Wednesday night.   The St. Clair County Drug Task Force seized heroin, crack cocaine and other items in the 2000 block of Military Street in Port Huron, according to a news release.  Police say they found $600 in heroin, crack cocaine, $404 in cash, digital scales, multiple electronic items and a starter pistol.  Possible charges could include possession of heroin with intent to deliver, possession of crack cocaine, maintaining a drug house and frequenting a drug house.  The man was on probation and is being held in the St. Clair County jail.