President Donald Trump’s immigration enforcement efforts have made a significant impact on border security and arrest numbers over his first 10 months in office, according to Department of Homeland Security data released Tuesday.

The Border Patrol made 310,531 arrests during the fiscal year that ended Sept. 30, a decline of 25 percent from 415,816 a year earlier, according to Customs and Border Protection (CBP). Typically used as a proxy measure for illegal immigration, border arrests fell to their lowest level since 1971.

In the interior of the country, immigration agents carried out 143,470 arrests, an increase of 25 percent from 114,434 a year earlier, according to figures from Immigration and Customs Enforcement (ICE).

The year-end arrest data reflects the administration’s crackdown on illegal immigration, which expanded the number of unauthorized aliens that could be targeted for arrest and deportation. Within a few weeks of taking office, Trump lifted the previous administration’s restrictions on which illegal immigrants would be a high enforcement priority, making anyone in the U.S. illegally a potential subject for deportation.

It is unclear how much of the drop in border apprehensions can be attributed to Trump’s new enforcement priorities, but anecdotal evidence suggests it has had a deterrent effect on potential border crossers. A DHS report released earlier this year also indicates the Border Patrol has become much better at interdicting illicit border crossings and deterring repeat offenders. Today, enhanced border security deters about 55 to 75 percent of would-be second-time offenders, versus 10 to 40 percent a decade or two ago.

“We have clearly seen the successful results of the president’s commitment to supporting the frontline officers and agents of (the Department of Homeland Security) as they enforce the law and secure our borders,” said DHS Acting Secretary Elaine Duke, according to the Associated Press.

Fewer border arrests translated to a 6 percent drop in overall deportations from the previous year. That decline was the result of fewer people being caught at the border, and was offset by a significant increase in “interior removals,” according to ICE.

The number of people deported after being arrested in the interior of the country climbed 25 percent to 81,603, up from 65,332 the previous year. In the period between Trump’s inauguration and the end of the fiscal year, interior removals jumped 37 percent compared to the same period a year earlier.