On Tuesday, investigators arrested Thomas Richard Sutherland, 42, at the Saskatoon correctional facility.
Sutherland was charged with the unlawful confinement and aggravated assault of the Métis woman, 30, who has been missing since 2020.
Police say Sutherland was incarcerated on an unrelated sentence at the time of his arrest and remains in custody after appearing in Saskatoon Provincial Court Wednesday.
Police are expecting additional arrests as the investigation progresses.
The police have also announced forensic anthropologist, Ernie Walker of the University of Saskatchewan and officials from the Water Security Agency will be involved in an extensive search along the South Saskatchewan River for Gallagher.
The search will be conducted near St. Louis, Sask., 120 km northeast of Saskatoon.
A number of civilian search and rescue personnel, members of the provincial protective services, and K-9 teams from the Calgary Police Service will be assisting in the search.
The search is planned over four days, concluding on Sunday, Oct. 2. Police are asking the public to avoid the area as it is a potential crime scene.
Two people are charged with first-degree murder in Gallagher’s death – Cheyann Crystal Peeteetuce, 29, and Robert “Bobby” Thomas, 27.
Another four people are charged with offering an indignity to human remains. None of the accused have yet to enter a plea to their charges.