Figures released by the Kenora OPP shows there was almost 400 hours of overtime racked up by officers last month.
That was almost four times higher than the month of November.
Staff Sergeant Paul Van Belleghem says a murder investigation in Lakeside took up a huge amount of their resources.
Van Belleghem says the province picks up the cost for any specialist units that have to be brought in, but the municipality has to pay the rest.