CALGARY -- Police in Calgary say they've made a last sweep of the home owned by a couple who have been missing along with their five-year-old grandson since last month.

Police say they have completed their search for evidence in the home of Alvin and Kathy Liknes.

The couple and their five-year-old grandson Nathan O'Brien disappeared on June 29 and police have said there is evidence a violent incident occurred in the home.

Police say they're continuing to search a northwest Calgary landfill and a rural property and some of its surrounding lands near Airdrie, north of Calgary.

Police have no suspects but have designated a resident of the rural property, Douglas Garland, a person of interest.