New York City allowed a company that controls thousands of phone booth advertising displays in the city to install beacon transmitters in numerous undisclosed locations in Manhattan.

Beacons are Bluetooth devices that emit signals to smartphones; in theory they can be used to track people's movements and push advertisements. The installation of the beacons, manufactured by San Diego company Gimbal, came without public knowledge or consultation, according to a report from BuzzFeed.

In light of the report, City Hall has apparently asked the company responsible — Titan — to remove the transmitters.

See also: People Are Willing to Give Away Their Personal Data for a Cinnamon Cookie

Titan claimed the beacons were installed for maintenance purposes, but in at least one instance they were used to push ads to mobile phones for Tribeca Film Festival attendants.

The beacons can also pick up location data, but Titan denied to the New York Daily News that it was using the beacons to collect data from passing people's phones.

The beacons are being used on a test basis (to experiment with the technology's effectiveness) — "any explicit commercialization" would require further city deliberation, according to the New York Department of Information Technology and Telecommunications.