The FBI can access hundreds of millions of photographs that can be used with facial recognition technology, a government watchdog said Tuesday.

Gretta Goodwin, a representative from the Government Accountability Office, told House lawmakers the FBI has access to about 640 million photographs, according to the Associated Press.

The FBI can access the photos through its database of mugshots and its contracts with 21 states to access drivers licenses, among other databases, Goodwin said.

Kimberly Del Greco, a deputy assistant director at the FBI, said the Bureau has strict policies in place for using facial recognition technology.

At the House Oversight Committee Hearing, both Democrats and Republicans expressed concern about the technology.

Del Greco maintained that the technology is only used during an active FBI investigation or an assessment before a formal investigation is launched.

“Facial recognition is a tool that, if used properly, can greatly enhance law enforcement capabilities and protect public safety,” she said.

Civil liberties groups have asked lawmakers to prohibit the technology until Congress determines whether its use is permissible.