Campaigners have raised privacy concerns over a facial recognition database being developed by the FBI that could contain 52m images by 2015.
The civil liberties group Electronic Frontier Foundation (EFF) obtained information about the project through a freedom of information request.
It said it was concerned that images of non-criminals would be stored alongside those of criminals.
The FBI say the database will reduce terrorist and criminal activities.
The facial recognition database is part of the bureau's Next Generation Identification (NGI) programme which is a large biometric database being developed to replace the current Integrated Automated Fingerprint Identification System (IAFIS).
The programme, which is being rolled out over a number of years, will offer "state of the art biometric identification services" according to the bureau's website.
As well as facial recognition images the programme is being developed to include the capture and storage of finger prints, iris scans and palm prints.
EFF said that the records it had seen showed the facial recognition element of the NGI already contained 16m images by 2013 and had the capability to contain as many as 52m by 2015.
In the current system, the fingerprints of criminals and non-criminals are kept in separate databases. Non-criminals may have their prints stored by the FBI if they have applied for a job that requires fingerprints for a background check.
However, under the new system if a candidate is asked by an employer to submit a photo along with their fingerprints this will now be stored by the FBI, too. The difference is that all photos will be stored on the same database regardless of whether someone has been arrested for a crime.
"This means that even if you have never been arrested for a crime, if your employer requires you to submit a photo as part of your background check, your face image could be searched - and you could be implicated as a criminal suspect, just by virtue of having that image in the non-criminal file," said the EFF.
It says documents from the FBI show that 4.3m photos contained in the database by 2015 will be for non-criminal purposes.
The group also cites research that shows the risk of falsely identifying someone increases as the size of the dataset being examined increases.
"This means that many people will be presented as suspects for crimes they didn't commit."
At a US senate subcommittee meeting held in 2012 to discuss the privacy implications of facial recognition technology, the official in charge of the NGI programme at the time said the the FBI intended to limit the system to criminal information.
It was also stressed that annual audits of local agencies' systems will be carried out to "detect any type of misuse" and that the FBI would back this up with their own audits.
The EFF points out that the Privacy Impact Assessment for the facial recognition element of NGI has not been updated since 2008.
"This is not how our system of justice was designed and should not be a system that Americans tacitly consent to move towards," the EFF said.