Apple's already contentious relationship with China has just taken a turn for the worse. The Wall Street Journal is reporting that the computer giant has turned up on a list of companies named in a Chinese porn probe for allegedly offering illicit material on their web sites and app stores.

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In total, the investigation is looking at 198 Web sites and several app stores beyond Apple's.

Based solely on a rough Google-translated version of the People's Daily piece, it's difficult to tell exactly what type of X-rated material has raised China's hackles.

Apple is typically quite cautious about letting any "adult" content get through its app store approval process. And the company is usually quick to bar any app that violates its guidelines.