Two more US lawmakers are calling for investigations into TikTok as a possible risk to national security, Tony Romm and Drew Harwell at The Washington Post reported.

Senate Minority Leader Chuck Schumer and Sen. Tom Cotton cooperated across political parties to cowrite a letter asking intelligence officials to investigate TikTok on Wednesday. The letter was addressed to director of national intelligence Joseph Maguire, and suggests that the Chinese-owned app poses a “potential counterintelligence threat we cannot ignore,” according to the Post.

"I'm concerned TikTok is just another avenue for the Chinese Communist party to conduct espionage activities in the United States and I look forward to hearing Acting DNI Maguire's assessment of this platform," Senator Cotton told Business Insider through a spokesperson.

TikTok did not respond to a request for comment.

This isn't the first time TikTok has been called out by US senators. Earlier this month, Sen. Marco Rubio asked the federal government to investigate the short-form video app, based on what he called "ample and growing evidence" that the platform censors content "in line with China's communist government directives," even for US-based users.

Sen. Rubio's complaint came only a few weeks after The Guardian reported on internal TikTok documents that advised moderators to censor content that could anger the Chinese government, including references to an independent Tibet and Tiananmen Square. A TikTok spokesperson told The Guardian that those guidelines were no longer in use as of May. A spokesperson told Business insider that the Chinese government does not have control over how TikTok operates, because the app doesn't exist in China - the Chinese version of the app is call Douyin. The spokesperson did not clarify, however, how requests from TikTok's parent company, ByteDance, a China-based company, are handled by the US TikTok team.

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US tech companies have also slammed TikTok over censorship allegations. In a speech at Georgetown last week, Facebook CEO Mark Zuckerberg said "While our services like WhatsApp are used by protesters and activists everywhere due to strong encryption and privacy protections, on TikTok, the China-based app growing quickly around the world, mentions of these same protests are censored, even here in the US," Zuckerberg said. "Is that the internet we want?"

TikTok has been working to combat the bad press over censorship. Earlier this month, it announced a new team to "further increase transparency around our content moderation policies and the practices we employ to protect our community," which included two former US lawmakers. The video app is growing quickly, and jumped to the top free non-gaming app, with an estimated billion users worldwide.