The revelation of a massive US citizen photo database fanned the flames of debate about the highly controversial high-tech solution to crimes, which can possibly become the culprit in mass wrongful arrests and privacy violations.

US lawmakers are calling for a nation-wide moratorium on facial recognition technology after a massive database of 640 million photos gathered by the Federal Bureau of Investigations (FBI) was revealed during a hearing on Tuesday.

Speaking before a House Oversight and Reform Committee, Government Accountability Office (GAO) representative Gretta Goodwin revealed that the FBI has access to some 640 million photos of US citizens, including 36 million mugshot photos and 21 state driver’s license directories. The revelation sparked bewilderment amongst the lawmakers.

“640 million photos,” repeated Rep. Jim Jordan (R-Ohio), the ranking member of the Committee. “There are only 330 million people in the country.”

While the FBI emphasizes it uses the vast database only to solve crimes, lawmakers got worried. Panel members accused the FBI of failing to implement “adequate privacy and accuracy guardrails” recommended by GAO three years ago before deploying the facial recognition technology across the nation, according to The Hill.

“Although the Committee has not called for a broad moratorium at this stage, I personally feel that we should consider it, and we will be continuing our robust bipartisan oversight of this issue to develop common-sense, concrete reforms that the whole Committee can support,” panel chairman Elijah Cummings told reporters.

The main concern regarding facial recognition technology is its predisposition for failure which bears signs of discrimination. Civil rights groups cite studies that claim the existing technology makes mistakes when analyzing certain populations at higher rates than others. Besides, there are questions regarding how the government is handling private data.

“We do have to have a pause on the implementation of facial recognition at a federal level ... until we make sure that it’s not violating our Fourth Amendment rights and civil liberties,” says Rep. Mark Meadows (R-N.C.), the chairman of the conservative House Freedom Caucus. According to the Fourth Amendment to US Constitution, US citizens have a right “to be secure in their persons, houses, papers and effects, against unreasonable searches and seizures.”

Currently, San Francisco - which, ironically, is the home to US main technology hub - is the only city across the US which has banned facial recognition. Several other cities, including Somerville, Massachusetts, are mulling taking this step, The Hill report says.

“The technology and the ethics have not meshed perfectly, and we need to get this right,” says William Lacy Clay, Democratic Representative from Missouri. “It doesn’t need to be a moving target. We need to be sure about identification because making a mistake could ruin someone’s life.”

The day before the hearing, a coalition of more than 60 activist groups, led by the American Civil Liberties Union (ACLU), sent a letter to the committee calling for a “federal moratorium on face recognition for law enforcement and immigration enforcement purposes until Congress fully debates what, if any, uses should be permitted.”