FBI Director Christopher Wray said Tuesday at a House committee hearing that China has stolen more American data “than every other nation combined.”

“China’s vast hacking program is the world’s largest, and they have stolen more Americans’ personal and business data than every other nation combined,” Wray said at the House Homeland Security Committee’s annual worldwide threats hearing.

The director, who served as an assistant attorney general under former President George W. Bush, emphasized that the U.S. has a “national security concern” when it comes to China.

Wray referenced the prevalence of TikTok and its parent company ByteDance, based in China, as one major intelligence concern.

“They include the possibility that the Chinese government could use to control data collection on millions of users or control the recommendation algorithm, which could be used for influence operations if they so chose or to control software on millions of devices, which gives the opportunity to potentially tactically compromised personal devices,” Wray said of the problems posed by TikTok.

There are still unresolved questions about data sharing between Chinese companies and the government in Beijing, said Wray, adding that “there’s a number of concerns there as to what is actually happening and actually being done.”

Homeland Security Secretary Alejandro Mayorkas and National Counterterrorism Center Director Christine Abizaid also testified at Tuesday’s hearing.