Arrests of illegal aliens along the U.S.-Mexico border ticked up in June but remained well below the number recorded in the same month last year, according to government figures released Friday.

Data from Customs and Border Protection shows that 21,659 people were arrested trying to illegally cross the Southwest border last month, a 9 percent jump from May, when the total was 19,962.

Even with the rise, June arrests were down 53 percent year-over-year. CBP also reported that year-to-date arrests at the border are 19 percent lower in FY2017 than the same period in FY2016. The figures include both apprehensions by Border Patrol agents and individuals deemed inadmissible at points of entry.

The number of arrests of illegal border crossers is often used as a proxy for the overall level of illegal immigration across a given time period. Illegal immigration across the Southwest border is usually higher during winter and spring.

The month-to-month uptick for June, the second straight month that arrests have risen, bucks a six-year trend in which immigration arrests have declined from May to June. While it is too early to tell if the recent increase marks the beginning of a bigger surge, the rising arrest figures could give the Trump administration fresh ammunition to argue for its border security agenda, especially the president’s call to build a wall along the entire U.S.-Mexico border. (RELATED: Border Patrol Chief Reveals When Border Wall Construction Will Begin)

On the other hand, the border wall could become a victim of Trump’s initial success in reducing the flow of illegal immigration across the Southwest border. The total number of apprehensions at the border and ports of entry has fallen to a six-year low in each of the five full months since Trump took office, causing some lawmakers to question whether an uninterrupted, border-spanning barrier is necessary.

Border arrests are on track to reach about 321,000 for all of FY2017, which would be 21 percent fewer than in FY2016.

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