03/29/2015 03:16 EDT | Updated 05/29/2015 05:59 EDT

Nathan O'Brien Case: Police search for evidence on Douglas Garland's property

Calgary police and RCMP are once again searching for evidence on the property of the man accused of murdering Nathan O'Brien, 5, and his grandparents, Alvin and Kathy Liknes.

It's unclear what led police back to Douglas Garland's property but investigators could be seen loading what looks like boxes into unmarked vans today and taking photos.

They're also searching the area and buildings around the home.

Plain clothes and uniformed officers, including members of the tactical team poured through the property throughout the day.

Neighbours say Garland's parents have been living in their home since police held it for several weeks back in the summer.

RCMP remain on scene, at the head of the long driveway guarding the rural property northeast of Airdrie.

Police say investigators are searching the property to collect additional evidence to support the upcoming court case. They do not have any new information in regards to the location of the victims. 

Nathan and his grandparents were last seen at a home in the southwest Calgary community of Parkhill on June 29, 2014. Their bodies have not been recovered, but Calgary police say the evidence indicated the three were dead.

Garland was arrested and charged with two counts of first-degree murder and one count of second-degree murder last July.

Garland's preliminary trial is set to begin in May.