Recently TikTok’s popularity has exploded worldwide, and so has scrutiny over the app’s parent company ByteDance and its relationship to the Chinese government. Now Reuters reports that the Committee on Foreign Investment in the United States (CFIUS) has opened a national security review of the company, because it had not sought approval to make its $1 billion acquisition of Musical.ly in 2017.

US lawmakers have expressed concern’s over the app’s ability to collect data, while the company responded saying “TikTok is committed to being a trusted and responsible corporate citizen in the US, which includes working with Congress and all relevant regulatory agencies.” The report notes that Musical.ly founder and now-head-of-TikTok Alex Zhu recently began to report directly to ByteDance CEO Zhang Yiming, which could help separate it from the company’s other holdings. Meanwhile, ByteDance just announced plans for its first smartphone.

TikTok allegedly asked its moderators to pull mentions of topics like the Tiananmen Square massacre, Tibet’s calls for independence and other content that challenges the Chinese government’s version of events. The service said it had retired the guidelines in May and that it had been using a “blunt approach” to minimizing drama on TikTok that included banning talk of all topics it deemed controversial, not just those from China.

An American TikTok spokeswoman talking to Reuters maintained that the Chinese government “does not request” censorship on its service. American data is stored in the US, she added, and China wouldn’t have jurisdiction over TikTok since it isn’t used there. Chinese residents instead use Douyin, a virtually identical app that is subject to Chinese censorship.

Whether or not there’s merit to the claims, Rubio has momentum on his side. The US just added eight Chinese tech companies to its Entity List over their help with China’s suppression of Muslim minorities. Moreover, Blizzard is facing a wave of criticism for banning an esports player that declared support for Hong Kong’s pro-democracy protests. Combine that with earlier actions against Huawei and ByteDance may face distrust even if its current practices are above-board.