WASHINGTON — Border Patrol agents are on track to apprehend up to 25 percent fewer undocumented immigrants crossing the U.S.-Mexico border in June compared to May, acting Department of Homeland Security Secretary Kevin McAleenan said at a press conference Friday.

In May, more than 144,000 immigrants were stopped crossing the border, including some presenting themselves legally at points of entry, the highest monthly total in 13 years.

The number of immigrants crossing into the Southwest United States typically drops off as temperatures heat up in the summer, but McAleenan said the decline was more than just seasonal.

Last year, there was a 17 percent decrease from May to June.

McAleenan said new agreements with Mexico, including increased interdictions of Central Americans crossing through that country to the U.S. and a policy of holding asylum-seekers in Mexico until their hearings in the U.S., contributed to the decrease.

He said there would be added locations in the coming weeks for holding migrants in Mexico while they await their asylum hearings in the U.S. Immigration attorneys recently argued in federal court the policy threatens migrants' lives by holding them in unsafe conditions.

McAleenan also said reports from the Clint border station near El Paso, Texas, about children being held in terrible conditions were "unsubstantiated."

The reports, from lawyers who had toured the facility and interviewed children there, detailed toddlers who had not had a clean change of clothes or diaper change, as well as teenage mothers wearing clothes stained with breast milk.

"Contrary to the reporting, children in CBP custody at the border are receiving access to key supplies, including toothbrushes, appropriate meals, blankets, showers as soon as they can be provided, and medical screening," McAleenan said.

On Friday, a federal judge asked to place a temporary restraining order on CBP for its handling of children in custody referred the matter to an independent party for mediation.