At least 50 Venezuelan men sent by the Trump administration to a prison in El Salvador had entered the United States legally, according to a review by the Cato Institute.

The report, published by the libertarian thinktank on Monday, analyzed the available immigration data for only a portion of the men who were deported to El Salvador’s notorious Terrorism Confinement Center (Cecot), and focuses on the cases where records could be found.

“The government calls them all ‘illegal aliens.’ But of the 90 cases where the method of crossing is known, 50 men report that they came legally to the United States, with advanced US government permission, at an official border crossing point,” Cato said in its report.