EXCAVATION of a mineshaft near Avoca will start this month in a bid to solve the 35-year-old mystery of a missing boy.Terry James Floyd, 12, disappeared from a country road at Avoca on Saturday June 28, 1975.He was last seen at the intersection of the Pyrenees and Sunraysia Highways about 5pm that day.A 2001 coronial inquest found Terry had likely died from unknown causes at an unknown place at an unknown time.Terry's brother Daryl, who was 10 at the time of Terry's disappearance, believes an old mineshaft at Bung Bong may hold the answer to the mystery.Information he has received in recent months has led him to believe his brother's body may have been dumped down the shaft.He said the search for Terry had taken a toll on his family.He said the stress had contributed to the premature death of his mother, Dorothy Floyd.She died, aged 56, 12 years to the day after Terry went missing.''Every year that comes around we don't have just the one anniversary for Terry it's also my mum's anniversary as well,'' Mr Floyd said. Mining records indicate the mine, which is in a state forest, was last active in 1920. But it was used as a dump for sewerage in the 1960s and early 1970s.Mr Floyd has the approval of Victoria Police and the Department of Sustainability and Environment for the excavation.He also has permission from the South Australian mining company which holds the lease on the mine.A Maldon-based mine excavation company will perform the excavation.Once the excavation begins, a vet will be on site to identify animal bones at the site.In the event any human remains are found, police will be called in.