SHANGHAI — The video app TikTok on Wednesday reversed its decision to block an American teenager who posted a clip in which she discussed the mass internment of minority Muslims in China, and acknowledged that its moderation system had overreached in shutting her out of her account.

The incident raised fresh concerns about whether TikTok, which is owned by the Chinese tech giant ByteDance, muzzles its users in line with censorship directives from Beijing — an accusation the company has denied.

TikTok said the teenager, Feroza Aziz, 17, had been barred from using her personal device to access the app, but not because of her video this past week about China’s detention camps. Rather, the company said, it was because she had used a previous account earlier this month to post a clip that included a photo of Osama bin Laden.

After TikTok banned that account for terrorist imagery, Ms. Aziz used a different one to post her video about the plight of Muslims in China. As the second video began to go viral, TikTok on Monday blocked more than 2,400 devices associated with accounts that had been banned for terrorist content and other malicious material, in what it called a scheduled enforcement action.