Canada’s privacy commissioner has begun a probe into billboards that use facial detection technology for targeted advertising.

The billboards, located near Toronto’s Union Station, reportedly analyze only the age and gender of passerbys, according to their owner, Cineplex Digital Media (CDM). They’re part of a growing wave of technology that uses cameras, large databases and in some cases artificial intelligence to survey people in public.

The debate began after a Reddit user posted last month about the billboards’ alleged facial detection capabilities. The Reddit post reportedly included an image of a disclaimer about the facial detection displayed on the billboard.

CDM has reportedly said that no personal data or images are kept and that the billboards process data within milliseconds.

Vito Pilieci, a spokesperson for Privacy Commissioner of Canada Philippe Dufresne, said that the office will investigate whether the billboards are legal under the country’s Personal Information Protection and Electronic Documents Act, which regulates private-sector companies.