TORNILLO — The Trump administration is opening a new 2,500-bed holding facility for adult migrants here, constructing a large, soft-sided structure close to the U.S.-Mexico border on the former site of a controversial shelter for migrant children, officials said Friday.

Roger Maier, a spokesman for Customs and Border Protection, confirmed that work to build the facility began this week. He said it will be designed to hold single adults who have crossed the border and have been taken into custody — it will not hold family units or unaccompanied children — and that it will “provide relief for overcrowded Border Patrol” stations as the agency awaits transferring the migrants to Immigration and Customs Enforcement custody.

“CBP anticipates populating the facility in late July or early August,” Maier said.

The new adult holding facility is being built at the Marcelino Serna Port of Entry, about 30 miles southeast of El Paso. The port is named after Serna, a Mexican immigrant who lived in El Paso and, as a U.S. Army soldier, became a decorated World War I hero.

That port was the home of a temporary shelter for unaccompanied migrant children from June 2018 to January 2019. It held more than 2,700 children at its peak in December, drawing repeated protests and becoming a focal point for critics of the administration’s border policies.

The child shelter closed in January after the Trump administration loosened some requirements it had created for potential sponsors offering to care for unaccompanied migrant children. A short time later, a large surge of Central American children began arriving at the border, and the administration expanded a temporary child facility in Homestead, Florida, and opened a new one recently in Carrizo Springs.

CBP officials said single adults at the new facility will be provided three daily meals, showers, medical services, laundry, custodial services and temperature controls.

Such CBP facilities in the past have been used to house migrants for less than 72 hours, but that has changed in recent months as the number of families crossing the border grew. Migrants have been held for weeks or months in facilities not designed to hold them that long, drawing increasing criticism from congressional Democrats.

Vice President Mike Pence visited such a facility in McAllen on Friday, seeing hundreds of migrants crammed behind caged fences, some who said they were hungry, thirsty or were in need of a shower. Some said they had been there a month or longer. Squalid conditions at border facilities have drawn widespread concern as the migrant flow across the border has surged to more 100,000 per month this year, at times overwhelming the U.S. immigration system.

The new holding facility in Tornillo came as a surprise to Georgina Pérez, a member of the State Board of Education who lives here. She said residents had not been notified that the facility was under construction and was staffing up.

“It’s 2019, and we’re still treating some people as less than human,” said Pérez, a Democrat who was a critic of the child detention facility.

Border crossings fell 28% from May to June, something the Trump administration attributes to increased Mexican immigration enforcement and U.S. policies aimed at deterring migration. It is unclear whether that decline will be part of a trend, and with construction of new facilities, it appears the U.S. government is preparing for the influx to continue.