BERLIN — Data protection officials in Germany reopened an investigation into Facebook’s facial recognition technology Wednesday, saying the social networking giant was illegally compiling a vast photo database of users without their consent.
The data protection commissioner in Hamburg, Johannes Caspar, said he had reopened his investigation, which he had suspended in June, after repeated attempts to persuade Facebook to change its policies had failed.
‘‘We have no other option but to reopen our investigation,’’ Caspar said in an interview. ‘‘We have met repeatedly with Facebook but have not been able to get their cooperation on this issue, which has grave implications for personal data.’’
The social networking company’s decision to use analytic software to compile photographic archives of human faces, based on photos uploaded by Facebook’s users, has been controversial in Europe, where data protection laws require users to give their explicit consent to the practice. Instead of using such an opt-in system, Facebook assumes users will want to use facial recognition and requires them to opt out instead.
Caspar, who led Germany’s investigation into Google’s illegal collection of personal Internet data siphoned from residential Wi-Fi routers, said he had met with Facebook officials several times on the issue since he opened his investigation in June 2011.
The Hamburg regulator is demanding that Facebook destroy its photographic database of faces collected in Germany and revise its website to obtain the explicit consent of users before it creates a digital file based on the biometric data of their faces.
In their meetings, Facebook representatives acknowledged that the company was compiling biometric data on users, Caspar said, but have maintained that the practice is legal in Ireland, where Facebook’s European operation is incorporated.
Facebook said in a statement that it was not breaking EU law with facial recognition software, which prompts users to ‘‘tag,’’ or identify, people in photos uploaded to the service.
‘‘We believe that the Photo Tag Suggest feature on Facebook is fully compliant with EU data protection laws,’’ Facebook said. ‘‘During our continuous dialogue with our supervisory authority in Europe, the Office of the Irish Data Protection Commissioner, we agreed to develop a best practice solution to notify people on Facebook about Photo Tag Suggest.’’
Irish officials are concluding a second audit of the company’s data protection practices. Gary Davis, Ireland’s deputy data commissioner, said the agency was continuing its talks with Facebook and was hopeful of reaching a settlement on obtaining a consent agreement and on the status of existing photo archives compiled from European users.
Facebook, Davis said, had voluntarily agreed to suspend its tagging feature for Europeans who join the social networking site as of July 1.
The situation for others ‘‘remains under active discussion,’’ Davis said.