Facebook cofounder and ceo Mark Zuckerberg streaming his keynote at the virtual Facebook Connect conference.

The Department of Justice filed a complaint against Facebook on Thursday, accusing the social media giant of discriminating against U.S. workers in favor of foreign candidates with temporary visas.

The Trump administration contends that the tech company set up a distinct hiring process for such workers, including those with H-1B visas, at the expense of domestic candidates. H-1B visas allow foreign professionals with “specialized knowledge” to work in the U.S.

The tactics alleged in the suit include not advertising open positions on its web site and not accepting online applications, instead requiring mail-in applications. The positions at stake numbered more than 2,600 roles with average starting salaries above $150,000.

“Our message to workers is clear: If companies deny employment opportunities by illegally preferring temporary visa holders, the Department of Justice will hold them accountable,” said assistant attorney general Eric S. Dreiband of the Civil Rights Division in a prepared statement. “Our message to all employers — including those in the technology sector — is clear: You cannot illegally prefer to recruit, consider or hire temporary visa holders over U.S. workers.”

Facebook won’t comment on pending litigation, apart from issuing a public statement saying that “we dispute the allegations in the complaint.”

The charges follow a two-year probe into the company’s hiring practices from 2018 through September 2019.

The issue could have major ripple effects for Silicon Valley, which has historically leaned heavily on H-1B visas to ensure a steady stream of high-tech talent amid a hypercompetitive recruitment environment. Last year, some 65 percent of H-1B workers in the U.S. filled tech-related roles, and Facebook, Google and Amazon were among employers with the most H-1B workers.

The Trump Administration’s dim view of H-1Bs is nothing new, and indeed, resulted in a temporary ban on such visas, starting this summer through the end of the year.

The action sparked a Big Tech pushback, with companies including Amazon, Facebook, Apple, Twitter, Microsoft and Netflix filing an amicus brief to argue the ban in a California court. The companies called the move “fundamentally un-American” in their brief.

And yet, tech companies have been more stringent about the visas, with denial rates for H-1Bs going up significantly during Trump’s tenure, according to the National Foundation for American Policy.

According to government data from U.S. Citizenship and Immigration Services compiled by NFAP, denial rates for new H-1B petitions for initial employment jumped 29 percent through the second quarter of fiscal-year 2020, compared to 6 percent in 2015.