Chinese intelligence services have sent “thousands” of people to U.S. colleges under the guise of college students and professors, federal officials said.

“We want to encourage people to come here and study,” Andrew Lelling, the U.S. attorney for Massachusetts, told reporters Friday. “This isn’t about targeting everyone who’s a Chinese national. But there are thousands who are directly linked to a state-sponsored effort to steal intellectual property.”

That warning underscores the scope of China’s “economic espionage,” as the Justice Department terms it, as a tool for national security and economic threat. That threat is part of a broader effort by Beijing to take advantage of American colleges and universities, which provoked a backlash among U.S. officials.

“The message to all the schools is: One, be aware that you are a target,” John Demers, the assistant attorney general at the Justice Department, said during the briefing. “Universities also have a lot of people coming in and out: students, visiting professors who are here for a year ... You may not know the folks there as well as you do maybe in a company.”

According to the most recent State Department data, more than 363,000 Chinese students studied in the U.S. in 2017-2018, nearly a third of all international students enrolled at U.S. institutions.

FBI Director Christopher Wray warned last year that China was using “nontraditional” intelligence collectors to launch a “whole-of-society” threat against the U.S. Those worries found an echo among lawmakers who worry that Chinese educational programs are platforms for propaganda and influence operations, while Secretary of State Mike Pompeo has been warning European allies that Chinese tech giants such as Huawei and ZTE are also being used as spy assets.

“MIT is not accepting new engagements or renewing existing ones with Huawei and ZTE or their respective subsidiaries due to federal investigations regarding violations of sanction restrictions,” the Massachusetts Institute of Technology announced Wednesday.

DOJ officials emphasized that “Boston is a target rich environment” for Chinese espionage, given the multitude of colleges and corporations with sensitive intellectual property, but they also sought to avoid overstating the fear.

“What we’re trying to focus on is differentiating the folks who come here to present a threat from the folks who come here just to study," Demers said.