Google still stocks the app and has declined to comment publicly on it
Apple removed 500px from the App Store after customers complained of child pornography on the popular photo-sharing app, the company told TheWrap.
The Instagram competitor, which has been downloaded nearly a million times, was in "clear violation" of the stringent guidelines by which Apple governs its software offerings.
"We also received customer complaints about possible child pornography," Apple, which made the app available in October 2011, said in a statement. "We've asked the developer to put safeguards in place to prevent pornographic images and material in their app."
An Apple spokesman did not immediately respond to questions about when it began receiving complaints about the app.
The Android version of 500px remained on Google Play Wednesday afternoon.
"We don't comment on individual applications – however, you can check out our policies for more information," a Google spokesman told the BBC.
500px's chief operating officer Evgeny Tchebotarev said the company does not allow pornographic images within its ecosystem, though he said it allows some artful nudes. The app offers a "safe search" feature, turned on by default.
"If something is purely pornographic, it's against our terms and it's deleted," 500px's chief operating officer Evgeny Tchebotarev told TechCrunch.
Neither Google nor 500px responded to requests from TheWrap for comment.