SEATTLE — In late 2016, Amazon introduced a new online service that could help identify faces and other objects in images, offering it to anyone at a low cost through its giant cloud computing division, Amazon Web Services.

Not long after, it began pitching the technology to law enforcement agencies, saying the program could aid criminal investigations by recognizing suspects in photos and videos. It used a couple of early customers, like the Orlando Police Department in Florida and the Washington County Sheriff’s Office in Oregon, to encourage other officials to sign up.

But now that aggressive push is putting the giant tech company at the center of an increasingly heated debate around the role of facial recognition in law enforcement. Fans of the technology see a powerful new tool for catching criminals, but detractors see an instrument of mass surveillance.

On Tuesday, the American Civil Liberties Union led a group of more than two dozen civil rights organizations that asked Amazon to stop selling its image recognition system, called Rekognition, to law enforcement. The group says that the police could use it to track protesters or others whom authorities deem suspicious, rather than limiting it to people committing crimes.