Thieves have been most active in parking lots around the north end in Niagara Falls, as well commercial parking lots within the area of Montrose Road, McLeod Road, Pin Oak Drive and Canadian Drive.
Suspects are using battery operated power tools such as grinders and reciprocating saws to cut the converters off the bottom of the cars and trucks.
The stolen catalytic converters are then being sold for the metals they contain.
Anyone with information about these thefts is asked to contact police or crime stoppers.