The U.S. government may be considering placing additional restrictions on Americans traveling to China as relations between Washington and Beijing continue to sour. Last week the U.S. State Department issued new guidance for those intending to visit China, suggesting that U.S. citizens should “exercise increased caution” when making plans. According to a State Department press release, “Chinese authorities have asserted broad authority to prohibit U.S. citizens from leaving China by using ‘exit bans,’ sometimes keeping U.S. citizens in China for years.” People with dual citizenship in the U.S. and China are also particularly vulnerable to harassment, as China does not recognize this status and as such often prevents dual citizens from contacting U.S. consulates for assistance.

Currently, the State Department has categorized China as a “level two” risk, which is only slightly elevated. However, Chinese authorities may have a more significant presence in places like the Xinjiang Uyghur and the Tibet Autonomous Region, according to a report from Reuters. The heavy police presence in these areas could mean an increased likelihood of foreign passport holders getting harassed.

Several American politicians applauded the State Department’s advisory on Twitter.

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Although China and the United States have been feuding for some time—over everything from fisheries to tariffs—the latest escalation of tensions leading to these travel advisories likely stems from the arrest of Chinese national Meng Wanzhou, the chief financial officer of Chinese telecommunications company Huawei. According to a report by Al Jazeera, Wanzhou’s arrest was carried out on behalf of the U.S. China promptly retaliated; Canadian officials claim that 13 of its citizens have since been arrested and are being held in China. U.S. authorities are attempting to extradite Wanzhou and have her charged with attempting to subvert American sanctions placed on Iran.

China is holding Americans captive as well. The family of Liu Changming, the former executive of China’s Guangzhou Bank who is currently wanted by Chinese officials in connection with financial crimes, are all being prevented from leaving the country. The family, which includes Liu’ wife Sandra Han, his son Victor, and his daughter Cynthia, are all American citizens and entered the country using their U.S. passports. Liu himself has not been heard of since 2007 when he disappeared, according to a report from Business Insider.