TORONTO — Scott Cresswell was behind the wheel of an unmarked white police truck as he drove across the Greater Toronto Area looking for compounds that might be used to hide stolen vehicles.

The York Regional Police detective entered a crowded commercial zone in Mississauga, Ont., where dozens of cars were parked, scanning for suspicious signs. He then drove to a neighbourhood outside the Halton Hills region, where a large, isolated home sat near farmland, surrounded by a fenced yard.