Absolutely. We know that from reputable studies not only in Canada but from around the world.
Specific to first nations children, there is a study called the “Canadian Incidence Study of Reported Child Abuse and Neglect”. Over three successive cycles of that study, with an error rate of less than .001—which is less than 1% and really the lowest possible rate of error you can get in a study—it says that the three factors driving the overrepresentation are poverty, poor housing, and substance misuse, all factors that we can do something about, thankfully, with culturally based and targeted interventions.
Unfortunately, that's significantly hampered by the inequalities in child welfare funding.