The Paris metro authority is testing CCTV software to detect whether travelers are wearing face masks.

It’s part of the city’s efforts to end lockdown and help prevent the spread of COVID-19, but it’s raised concerns from the government’s privacy watchdog.

The authority began a three-month test of its software from French tech company Datakalab this week at the Chatelet-Les-Halles station in the heart of Paris, normally used by about 33 million passengers per year. Monitors will have access to a dashboard with the proportion of riders believed to be wearing masks.