Police say they have uncovered hundreds of stolen cars and vehicle parts in a scrap yard north of Montreal, in what may be the biggest car-theft operation in Canadian history.

"It is probably the biggest seizure of stolen cars from a recycling business in Canada," Laval police spokesperson Nathalie Lorrain told CTV Montreal.

The investigation began during a routine patrol of the area, located in Duvernay, Laval. Officers said they spotted suspicious activity and did a spot check, turning up three stolen vehicle identification numbers.

Police then obtained a warrant to search the entire 100,000 square-foot-scrap yard.

Early estimates suggest more than 700 stolen cars, including luxury vehicles. But police will only have an exact number after a thorough search of the yard, which could take a week.

"Some of the cars here were brand new, probably out of either a lot or wholesaler and with no mileage," said Lorrain.

"Some of them had more mileage. But there were a lot of luxury SUVs, a lot of cars like Mercedes, Jaguars, you name it. They're all here."