TikTok head Alex Zhu canceled meetings with U.S. lawmakers this week that were scheduled after concerns were raised that the Chinese company poses a national security threat.

TikTok came under heightened scrutiny after it acquired Musical.ly, an app popular among young Americans for creating and sharing short lip-sync videos.

TikTok is itself a video sharing app geared towards young Americans, and it’s acquisition of an additional app that collects data and personal information on minors has increased the concern that TikTok is a national security threat.

“What is the real reason TikTok has cancelled my meeting with CEO Alex Zhu?” Republican Senator Marsha Blackburn tweeted. “What are they really doing with your data and what type surveillance are they conducting on your precious children? TikTok — you owe us answers.”

TikTok has cancelled scheduled meetings with U.S. lawmakers at the last minute before, and has also declined to participate in Republican Senator Josh Hawley’s congressional hearing to explore the security and censorship risks TikTok poses.

Zhu cancelled one meeting with Hawley this week as well.

“NEWS: @tiktok_us just cancelled their meeting with me this week. Not willing to answer questions,” tweeted Hawley, who also asked “Get a call from Beijing?”

Chinese companies are notoriously controlled by the Communist Party in Beijing.

TikTok was downloaded 110 million times in the U.S. last year alone, surpassing Instagram as a growing platform among young users.

TikTok was caught censoring content last month when an account belonging to a 17-year-old high school student was suspended after she posted a viral video addressing human rights abuses against China’s minority Muslim population.

The Xinjiang region of China has a population of 22 million with about 10 million Uyghur Muslims, and an estimated 1 million Uyghur Muslims are being held by Chinese authorities in prisons called “re-education centers” by communist Chinese government. China is reportedly sending men to sleep in the same beds as Uighur Muslim women while their husbands are in the prison camps, causing untold numbers of rape.

Sayragul Sauytbay, an ethnic Kazakh Uighur woman who fled a Xinjiang detention camp, told Haaretz last month that she witnessed a gang rape and medical experiments on other prisoners. She said she was also subject to beatings and food deprivation because another prisoner hugged her.

In it’s own country, China has been using data collection to police it’s population in a variety of ways, including preventing citizens with a bad “social credit score” from using public transportation or flying on planes. A reported 2.5 million “discredited entities” were prevented from purchasing plane tickets and 90,000 people from buying high speed train tickets in the month of July alone.

China also recently began using facial recognition for payment. The new payment method combined with China’s dystopian “social credit” score may lock dissenters out of the economy. Chinese citizens will also be forced to pass a facial recognition test that runs them through their social credit score database before being allowed to use the Internet.

Chinese citizens that speak out against the government in any way – even making comments on social media – are subject to arrest and imprisonment. Serious dissenters may even be subject to death via China’s mobile execution vans where organs are harvested and sold.