SAN DIEGO — Arrests for illegal border crossings from Mexico during August are expected to rise slightly from July, officials said, possibly ending a streak of five straight monthly declines, but the numbers are hovering near four-year lows.

Authorities made 54,000 arrests through Thursday, which, at the current rate, would bring the August total to about 58,000 Saturday, according to two U.S. Customs and Border Protection officials. The officials spoke on condition of anonymity to discuss information that has not been released.

The tally suggests that arrests could be bottoming out after being halved from a record 250,000 in December, a decline that U.S. officials largely attributed to Mexican authorities increasing enforcement within their borders. Arrests were more than halved again after President Joe Biden invoked authority to temporarily suspend asylum processing in June. Arrests fell to 56,408 in July, a 46-month low that changed little in August.

The steep drop from last year’s highs is welcome news for the White House and Democratic presidential nominee Kamala Harris, despite criticism from many immigration advocates that asylum restrictions go too far and from those favoring more enforcement who say Biden’s new and expanded legal paths to entry are too generous.

San Diego had the most arrests among the Border Patrol’s nine sectors on the Mexican border in August, followed by El Paso, Texas, and Tucson, Arizona, though the three corridors were close, officials said.

Arrests of Colombians and Ecuadoreans fell, which officials attributed to deportation flights. Mexico, Guatemala and Honduras were the top three nationalities.