The city of Boston spent $650,000 to test surveillance software during a music festival last year, using the technology to record concertgoers without their knowledge.
A city spokeswoman tells The Boston Globe that while there are no further plans to use the technology, future tests of systems with similar capabilities may also be done without notifying those being recorded.
Systems like the one tested at the Boston Calling festival have multiple purposes, from alerting police to abandoned bags to sorting people by height or skin color.
The city denied using the technology's ability to track individuals based on race or other characteristics.
While not illegal, civil libertarians say use of the technology without telling anyone raises privacy concerns.
The program was first reported in the alternative weekly DigBoston.