One man has been arrested in connection to an armed robbery at the Thomas Edison Inn.  The arrest was made by Port Huron Police when, through  a drug-related warrant search of a residence on the 800 block of White Street in Port Huron at about 9:30 p.m. Friday.  A 22-year-old Port Huron man police believe was the gunman in the armed robbery that occurred Thursday was arrested for maintaining a drug house and possession with intent to deliver drugs.   Three other men were arrested for frequenting a drug house. They were a 19-year-old Port Huron man, a 21-year-old St. Clair man and a 20-year-old Detroit man. All three were released from police custody.  Investigation into Thursday’s armed robbery at the Thomas Edison Inn continue.  Reports say 22-year-old Port Huron man and a 24-year-old and 20-year-old from Sault Ste. Marie were sharing a room at the inn when they opened the door to a man holding a semi-automatic handgun.  The gunman fled after the occupants of the room gave him a sum of money. The Port Huron man sharing the room also left the scene, and police believe he might have helped set up the robbery.