The U.S. government launched a national security investigation into the popular app TikTok on Friday — looking expressly into the Chinese company’s acquisition of the app Musical.ly. TikTok purchased the company for $1 billion roughly two years ago.

The Committee on Foreign Investment in the United States (CFIUS) is reportedly investigating the deal now in part because TikTok did not seek clearance from CFIUS when it acquired the company. CFIUS reviews are confidential.

In October, TikTok came under fire for hosting ISIS propaganda videos on the platform. On October 21, reports indicated that the service removed around two dozen accounts from the platform for posting extremist propaganda.

Its parent company, Bytedance, was also accused by lawmakers of censoring content on the platform at the request of the Chinese government. We’ve reached out to TikTok for comment and will update this story if we hear back.

In July, TikTok was also investigated by the U.K. government for how it handles personal information of children that use the platform. They examined in particular how it collects, handles, and uses that data.

Lawmakers in the U.K. were directly concerned with the open messaging system on the platform that can allow adults to contact children. The Federal Trade Commission (FTC) had similar concerns that the platform was not getting the correct consent prior to allowing children under 13 to use it.

“We are looking at the transparency tools for children,” Elizabeth Denham, head of the Information Commissioner’s Office (ICO) in the United Kingdom, said in July. “We’re looking at the messaging system, which is completely open, we’re looking at the kind of videos that are collected and shared by children online. So we do have an active investigation into TikTok right now, so you can watch that space.”

TikTok has a particularly young user base. Earlier this year it indicated that roughly 60% of its 26.5 million monthly active users in the United States are between the ages of 16 and 24.

In addition to TikTok, ByteDance also owns China’s most popular news aggregator, Jinri Toutiao. The app is financially backed by Japan’s Softbank, as well as venture capitalist and private equity firms Sequoia Capital, KKR, General Atlantic, and Hillhouse Capital.