07/14/2014 12:56 EDT | Updated 09/13/2014 05:59 EDT

Douglas Garland back in police custody as Nathan O'Brien search continues

Douglas Garland, who is named as a person of interest in the disappearance of five-year-old Nathan O'Brien and his grandparents, is back in police custody.

Sources close to the investigation say Garland is being questioned by police in connection with the missing family case.

The 54-year-old was staying at a motel in Airdrie, just north of Calgary, since he was released on bail on unrelated charges last Friday.

Nathan and grandparents Alvin and Kathryn Liknes have been missing since June 29. The Amber Alert is still active for the young boy, but the search is into its third week.

"As the days go by, it's simply a question of where could these people be that they could still be safe?" said Patrick Baillie, a forensic psychologist with Alberta Health Services.

"And while it is difficult to maintain optimism regarding a positive outcome, we're still hoping that there is some resolution for the family and for the community."

Police say after multiple searches, they have ended the investigation into the Parkhill home where the three Calgary family members were last seen.

The home belongs to Kathryn and Alvin Liknes.

Police say there was evidence a violent crime occurred in the southwest Calgary home.

The search for evidence will continue this week at the Spyhill Landfill in Calgary where investigators are still sifting through mounds of garbage.

Police will also continue to search an acreage in Airdie that belongs to Garland's parents.