Authorities in the United States have arrested 90 more foreign students for allegedly enrolling in a fake university set up by undercover agents from the Department of Homeland Security to reveal a “pay-to-stay” immigration fraud, The Detroit Free Press reported on Wednesday. They had arrested 161 such students in February and March.

Around 600 students, mostly Indians, were allegedly enrolled in the “University of Farmington”, which has now been closed. Out of the 250 students arrested, nearly 80% were granted voluntary departure and left the United States, while the rest have received a final removal order, the newspaper reported, citing a statement from the US Immigration and Customs Enforcement.

Prosecutors claimed that the students knew this was a fake university as there were no classes. The fake university had no staff or curriculum and was part of the Department of Homeland Security’s “Operation Paper Chase”. The 600 students collectively paid recruiters more than $250,000 to stay in the US, prosecutors said.

Eight recruiters were charged with participating in a conspiracy to help foreign citizens stay in the US illegally. The investigation reportedly dates back to 2015, but intensified in Donald Trump’s first month as president as part of a crackdown on illegal immigration.

The arrests have led to outrage on social media, with the #AbolishICE hashtag picking up on Twitter. Senator Elizabeth Warren, who is running for president from the Democratic Party, called it “cruel”.

“This is cruel and appalling,” she said on Twitter. “These students simply dreamed of getting the high-quality higher education America can offer. ICE deceived and entrapped them, just to deport them.”

The “pay-to-stay” scheme involves foreign nationals who purportedly enroll in fake institutions to falsely maintain their student visa status to allow them to continue to stay in the United States.