CALGARY – Investigators are returning to the scene of the crime in the disappearance of a five-year-old Calgary boy and his grandparents.

Police say they will sweep the property of Alvin and Kathy Liknes as part of a three-pronged attack today, searching for more clues.

The couple and their five-year-old grandson, Nathan O’Brien, disappeared from the home on June 29.

Police say there is evidence a violent crime occurred there.

Searchers also continue to comb the rural property of person-of-interest Douglas Garland near Airdrie, north of Calgary, as well as several surrounding acreages.

Police are also sifting through mounds of garbage at a northwest Calgary landfill.