In brief: When microblogging site Tumblr had its official iOS app removed from the App Store a few days ago, the company would only say that it was “working to resolve an issue” with the application. Now, the reason for its disappearance has been revealed: the discovery of child pornography on the platform.

A Tumblr spokesperson told CNET’s that the site keeps child pornography off its service by scanning every image “against an industry database of child sexual abuse material,” thereby filtering out and blocking such content.

During a routine audit, content was discovered that had not yet been included in the industry database, which meant it was able to pass through the image filter. notes that this is the reason behind the app’s sudden disappearance and lack of explanation: child pornography is a crime that requires coordination with law enforcement upon its discovery.

No word on when the iOS app might return to the App Store, but Tumblr says it is still working with Apple to help it happen. The Android version of the app has remained available on Google Play throughout.

Tumblr, which is a subsidiary of Verizon-owned Oath, has faced other issues over its content in the past. The Indonesian government briefly blocked it in March after the firm failed to remove pornographic material from the service.

Tumblr isn’t the only app to be removed from the App Store for this reason. Back in February, Telegram X vanished for a few hours after the store’s team was "alerted to illegal content, specifically child pornography." The material was likely being served via a third-party plugin used by Telegram.

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