WASHINGTON — The number of arrests by Border Patrol agents of people illegally crossing into the United States fell in May to the third lowest of any month during the Biden presidency, while preliminary figures released Thursday show encounters with migrants falling even more in the roughly two weeks since the president announced new rules restricting asylum.

The figures are likely welcome news for a White House that has been struggling to show to voters concerned over immigration that it has control of the southern border. But the number of people coming to the border is often in flux, dependent on conditions in countries far from the U.S. and on smugglers who profit from global migration.

Border Patrol made 117,900 arrests of people entering the country between the official border crossing points in May, Customs and Border Protection said in a news release. That’s 9% lower than during April, the agency said. The agency said preliminary data since President Biden’s June 4 announcement restricting asylum access shows arrests have fallen by 25%.

“Our enforcement efforts are continuing to reduce southwest border encounters. But the fact remains that our immigration system is not resourced for what we are seeing,” said Troy A. Miller, the acting head of CBP.

The U.S. has also benefitted from aggressive enforcement on the Mexican side of the border, where Mexican authorities have been working to prevent migrants from making their way to the U.S.-Mexico border.

The figures are part of a range of data related to immigration, trade and drug seizures that is released monthly by CBP. The immigration-related figures are closely watched at a time of intense political scrutiny over who is entering the country and whether the Biden administration has a handle on the situation.

Immigration is a top concern for voters, with many saying Biden hasn’t been doing enough to secure the country’s borders. Former President Donald Trump, the presumptive Republican nominee for president, has made immigration a cornerstone of his campaign by saying he’s going to deport people in the country illegally en masse and take other measures to crack down on immigration.

After Biden announced his plan to restrict asylum access at the southern border, opponents sued, saying it was no different from a similar effort under Trump.