Sen. Marco Rubio on Wednesday asked the U.S. government to open an investigation into TikTok, the wildly popular, Chinese-owned social media app, out of concern that the company is “censoring content” around the world to satisfy Beijing’s leaders.

Rubio (R-Fla.) requested a broad investigation into the company from the Committee on Foreign Investment in the United States, or CFIUS, which oversees foreign acquisitions for national security concerns. In 2017, TikTok’s parent company, Bytedance, purchased, which had a presence and user base in the United States, and later merged it with its own offering, creating the social media behemoth that has been installed by more than 1 billion people globally.

In his letter Wednesday to Treasury Secretary Steven Mnuchin, Rubio requested a full review of the national security implications of TikTok’s acquisition. “The Chinese government’s nefarious efforts to censor information inside free societies around the world cannot be accepted and pose serious long-term challenges to the U.S. and our allies,” he wrote.

In a series of tweets, Rubio added that he has asked the Trump administration to “fully enforce anti-boycott laws” that prohibit any person or “U.S. subsidiaries of Chinese companies” from “complying with foreign boycotts seeking to coerce U.S. companies to conform with #China’s government views.”

Rubio’s call follows a firestorm of recent criticism aimed at both Chinese censors and U.S. companies that have penalized people for voicing support for protests in Hong Kong, in hopes of avoiding the wrath of the government of the world’s second-largest economy. China penalized the National Basketball Association this week after a team leader posted a message supporting the protests, and the California-based video-game giant Blizzard Entertainment suspended a professional esports player for shouting “Liberate Hong Kong” during an interview.

TikTok’s lack of content related to the Hong Kong protests, which Chinese leaders have pushed to undermine, has raised fears that the platform is censoring ideas the government wants to suppress. In response, TikTok’s Beijing-based parent company told The Washington Post last month that the app’s U.S. platform was not influenced by the Chinese government, and that the lack of protest footage could be related to users’ view of the app as a place for entertainment, not politics. It declined to share any additional details about its content-moderation practices.

A spokesperson for TikTok did not respond to a request for comment on Wednesday. The Treasury Department also did not immediately respond to a request for comment.

Rubio’s quest for a CFIUS probe could resonate with the White House in the midst of its trade war with China, which has started to strain both countries’ economies. Last month, the Trump administration proposed new rules that would enhance the powers of CFIUS, particularly with an eye on scrutinizing Chinese investment in areas including technology.

TikTok content-moderation guidelines, revealed last month by the Guardian, showed that the app banned criticism of the Chinese government and discussion of historic events such as the Tiananmen Square massacre in 1989, during which the Chinese military killed thousands of people amid pro-democracy protests.

A TikTok spokesperson said the rules were no longer in use and reflected the app’s early days, when the company “took a blunt approach to minimizing conflict on the platform.” The spokesperson said the company understood “the need to be more transparent” in communicating its policies but has declined repeatedly to share its current guidelines for deciding which content is permitted or suppressed.

Some business and technology analysts share Rubio’s views, worrying that an encroachment of Chinese government control could threaten traditionally Western values supporting creative expression and freedom of speech. Technology analyst Ben Thompson said Tuesday that CFIUS should revisit TikTok’s acquisition and that “the current skepticism around all Chinese investment in the United States should be continued if not increased.”

“Attempts by China to leverage market access into self-censorship by U.S. companies should also be treated as trade violations that are subject to retaliation,” he wrote in his blog Stratechery. “Make no mistake, what happened to the NBA this weekend is nothing new: similar pressure has befallen multiple U.S. companies, often about content that is outside of China’s borders.”