The FBI has amassed more than 411 million photos as part of its vast facial recognition database, according to a government watchdog -- which in a new report criticized the system for its lack of safeguards and protections.

That includes millions of individuals' driving license photos, as well as photos of foreigners applying for visas, and criminal mugshots.

But the Government Accountability Office (GAO) criticized the FBI in a new report, published Wednesday, saying that the agency had not properly tested the system or balanced civil liberties and privacy.

The system kicked into operations in early-2015 after what appeared to be a relatively successful pilot. Agents would feed in a photo and the database would spring back between two and no more than 50 images of suspects, leaving the agent to make the final call on who the suspect might be.

But the GAO argued that there's no way to determine whether or not the returned images are any more accurate than the number of images rejected by the system.

That could lead to "potentially innocent individuals identified [that] could be brought in for questioning," which the report said "if false positives are returned at a higher than acceptable rate, law enforcement users may waste time and resources pursuing unnecessary investigative leads."

In one paragraph, the GAO said that the FBI's reliance on third-party data -- which the agency can't vouch for its accuracy -- could lead to missed investigative leads.

"The FBI has entered into agreements to search and access external databases -- including millions of U.S. citizens' drivers' license and passport photos -- but until FBI officials can assure themselves that the data they receive from external partners are reasonably accurate and reliable, it is unclear whether such agreements are beneficial to the FBI and do not unnecessarily include photos of innocent people as investigative leads," said the report.

In other words, the system as it stands opens up the possibility of automating a process of picking out faces that have nothing to do with an investigation -- opening up the likelihood that innocent people may be drawn up as suspects in ongoing criminal matters.

The Electronic Frontier Foundation (EFF), which was cited in the report, said on its blog following the report's release that it the findings were "shocking."

"Over and over, the FBI's secret data collection practices confirm why we need more transparency, not less. In the coming weeks, we'll be asking you to sign on to our comments to the FBI's proposal," said senior staff attorney Jennifer Lynch.

The Justice Dept. said it disagreed with half of the recommendations the watchdog made.