United States Customs and Border Protection observed a plummet in encounter numbers at the southern border in the days after President Donald Trump announced new security measures.

Ali Bradley, a reporter who covers the border for NewsNation, spoke to Department of Homeland Security sources who said that there were 1,940 encounters of illegal aliens reported by Border Patrol between Monday and Tuesday, and only 440 as of Wednesday evening.

That represents a substantial decline from the 4,000 encounters of illegal aliens reported by Border Patrol between the Friday and Sunday that came immediately before inauguration day.

The sources in the Department of Homeland Security said in comments to NewsNation that “this is what it is supposed to look like” at the border and attributed the change to “the Trump effect.”

There were 4,940 encounters reported by the Office of Field Operations between that Friday and Sunday, a statistic which plummeted to 930 between Monday and Tuesday, and to 45 as of Wednesday evening. Those encounters primarily come from the CBP One mobile app.

Trump administration officials shuttered the CBP One program within minutes of taking office. The website and social media pages for Customs and Border Protection featured an alert after the inauguration announcing that a feature of the CBP One app which “allowed undocumented aliens to submit advance information and schedule appointments at eight southwest border ports of entry is no longer available, and existing appointments have been cancelled.”