Reacting to concerns about the mass collection of photographs in police databases, U.S. lawmakers plan to introduce legislation to limit the use of facial recognition technology by the FBI and other law enforcement organizations.

The FBI and police departments across the country can search a group of databases containing more than 400 million photographs, many of them from the drivers' licenses of people who have never committed a crime. The photos of more than half of U.S adults are contained in a series of FBI and state databases, according to one study released in October.

Law enforcement agencies don't need a court-ordered warrant to search the database, members of the House of Representataties Oversight and Government Reform Committee noted during a hearing Wednesday.

Yet, the facial recognition system spits out false positive results about 15 percent of the time, with inaccuracies higher when police search for African-Americans and other racial minorities, critics said.

False positives could create serious problems for innocent people when FBI agents show up at their homes or workplaces, said Diana Maurer, director of homeland security and justice issues at the U.S. Government Accountability Office. A GAO report in mid-2016 recommended six steps the FBI can take to improve privacy protections, but the agency has moved to adopt only two of them, Maurer said.

Beyond false positives, widespread scanning of people's faces in public settings raise serious privacy questions, two privacy advocates said.

"Face recognition lets law enforcement recognize someone from far away and in secret," said Alvaro Bedoya, executive director at Center on Privacy and Technology at Georgetown Law. "Do you have the right to walk down the street without the government scanning your face?"

There are now few limits on law enforcement use of facial recognition technologies, Bedoya said. Law enforcement use of the technology lacks "meaningful" oversight or proper accuracy testing, added Jennifer Lynch, a senior staff attorney at the Electronic Frontier Foundation.

The FBI defended its use of facial recognition. The FBI limits its own searches to photographs collected in criminal investigations, and the matching results provide only an investigative tool, not a final determination of a suspect's identity, said Kimberly Del Greco, deputy assistant director of the FBI's Criminal Justice Information Services Division.

Facial recognition is a valuable tool in fighting crime, Del Greco added. "Our adversaries and the threats we face are relentless," she said. "The FBI must continue to identify and use new capabilities ... to meet the high expectations of the FBI to preserve our nation's freedom."

Concerns about the FBI's use of facial recognition technology came from both Republican and Democratic members of the Oversight Committee. Facial recognition offers many potential benefits, "but just because we can doesn't mean we should," said Representative Jason Chaffetz, a Utah Republican and committee chairman. "There are opportunities to have it misused or overused."

Lawmakers are working on a bill that would limit law enforcement searches of facial recognition databases, said Representative Jim Jordan, an Ohio Republican. During the hearing, lawmakers talked about requiring law enforcement agencies to get a court-ordered warrant to search the databases and possibly allowing U.S. residents who aren't criminal suspects to remove their photos from the databases.