Thieves are stealing catalytic converters and diesel particulate filters from pickup trucks in Edmonton.

"Due to the profitable nature of this crime, we believe several individuals or groups may be responsible for these thefts," Det. Vern Tuttle of the Edmonton police said in a news release.

Catalytic converters reduce harmful pollutants in exhaust systems. They contain small amounts of valuable metals such as platinum, palladium and rhodium.

Since Jan. 1, police have received 39 reports of thefts and attempted thefts of exhaust systems from diesel and gasoline trucks manufactured after 2008, including Ford F250s, F350s and F450s, Dodge Ram 3500s and larger commercial vehicles.

The thefts occurred at residential, commercial and industrial parking areas across the city.

"Vehicles left in parking lots over the weekend appear to be the most vulnerable," Tuttle said. "However, these thieves appear to be active any day of the week and have targeted some locations numerous times."

Investigators believe there are more victims and are encouraging anyone who has witnessed a theft to speak to them.