A diver edges into the Red River through an opening cut through the ice on Monday. (Sheila North-Wilson/CBC)

A pig cadaver is being lowered into Winnipeg's Red River in hopes it will give divers a better idea of where to look for the body of Nathaniel Thorassie.

The experiment will take place at about noon local time near the Disraeli Bridge, where six-year-old Nathaniel was with his brother, Ralph Chartrand, 10, when they both fell through the thin ice on Dec. 4.

Chartrand was rescued by a passerby, but Nathaniel could not be found.

Gordon Giesbrecht, a Manitoba professor renowned for his research on cold-water survival, will be helping police with the experiment, according to Sgt. Rob Riffel, head of the Winnipeg Police Service dive unit.

They will study how the current carries away the pig, which will be similar in weight and size to that of Nathaniel.

"We want to see if Nathaniel was possibly in a floating position, say a face-down position, if it's possible for the current to have taken him to the edge of the ice," Riffel said.

The dive team — members from the police service, the Winnipeg Fire Department and the Canadian Amphibious Search Team (CAST) — has also been using sonar equipment on loan from a Vancouver company.

The equipment identifies potential dive targets on the river's floor.

Police divers searched for Nathaniel's body over several days immediately after he fell through the ice, but were unsuccessful.

Volunteer divers from CAST and the Manitoba Search and Rescue Association (MSRA) then went into the water and searched over a couple of days, but also failed to find Nathaniel.

The police dive unit teamed with CAST members to resume the search on Dec. 21 and have been back on a daily basis since Jan. 2.