BERLIN — Data protection officials in Germany reopened an investigation into Facebook’s facial recognition technology Wednesday, saying that the social networking giant was illegally compiling a huge database of members’ photos without their consent.

The data protection commissioner in Hamburg, Johannes Caspar, suspended the inquiry in June, but said he reopened it after attempts to persuade Facebook to change its policies had failed.

“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,” Mr. Caspar said in an interview.

The company’s use of analytic software to compile photographic archives of human faces, based on photos uploaded by Facebook’s members, has been problematic in Europe, where data protection laws require people to give their explicit consent to the practice.