Migrants from Central America have been crossing the border by the tens of thousands in recent months, overwhelming agents from US Customs and Border Patrol, nonprofit groups, and local officials.
Those arriving have included families and unaccompanied children. The CBP reported apprehending nearly 133,000 people last month — as monthly totals have begun topping 100,000 for the first time since 2007.
The government has reported housing large numbers of detainees in structures meant for handfuls of people.
Experts say Central American migrants are arriving for a variety of reasons, including rising violence in their countries and the hope of a better economic future in the United States.
Drought and crop failure in their home countries caused by climate change is seen as another reason. Some reports have suggested a crackdown by the Trump administration — and a desire to get in the door before it closes — is another driver.
President Trump’s hard-line position
Trump, from the outset of his election campaign, has made a crackdown on illegal immigration a centerpiece of his presidency.
In addition to pushing for a massive border wall, his administration has sought to criminalize those entering the United States illegally, separate parents from their children, and drastically slow down the ability of migrants to apply for asylum in the United States.
More recently, his administration has imposed a plan to send thousands of asylum seekers back to Mexico to await their court proceedings. Under sustained pressure from Trump, Mexico has been stepping up its own migration enforcement in recent months.
The heartbreaking picture
A photo has ricocheted around the world of a father and young daughter who drowned in the Rio Grande River while trying to cross the southern border. The picture has broken hearts and stoked outrage as it has highlighted the dangers faced by the desperate pilgrimage of migrants to the border.
“It is very unfortunate that this happens,” President Andrés Manuel López Obrador of Mexico said at a news conference Tuesday. But as more migrants were being turned away by the United States, he said, “there are people who lose their lives in the desert or crossing the Rio Grande.”
Pope Francis saw the photos and was deeply saddened, a spokesman said. The photo also prompted denunciations from Democrats as Congress labored to pass a $4.6 billion humanitarian aid bill to help people detained while crossing the border.
The detained children
Outrage had already been brewing over reports of migrant children being held in pitiful conditions inside a windowless Border Patrol facility in Clint, Texas, with inadequate food, lack of medical care, no soap, and older children trying to care for toddlers.
Some had been locked for three weeks inside the facility, where 15 children were sick with the flu and another 10 were in medical quarantine. Many of the children were separated from extended family members like aunts and uncles who brought them to the border; others were teenage mothers with babies.
People moved by the stories showed up to donate boxes of diapers and even a Cookie Monster toy. The Clint facility was only an extreme example of the dire conditions reported at numerous locations where detainees have been held, and several children have died in US custody.
Video footage of a Justice Department lawyer arguing in federal court that the federal government was not legally required to provide toothbrushes, soap, or adequate sleep to detained migrant children added to the furor as it went viral last week.
Though the case dated to the Obama administration, the timing of her argument could not have been worse. Though some recognized it was the lawyer’s job to defend her client, the United States, others found her position indefensible.
By Tuesday, the media had obtained a private Facebook post in which the lawyer explained herself to her friends, saying she was limited in how much of her own opinion she could reveal, but “I will say that I personally believe that we should do our very best to care for kids while they are in our custody.”
The threat of raids
Trump also ratcheted up the tension and fear in immigrant communities nationwide in recent days with a wide-ranging threat to deport ‘‘millions’’ of undocumented immigrants. He later reversed his decision hours before the raids, which were actually expected to target 2,000 families in 10 major cities, were set to begin.
The standoff in Congress
Is help on the way at the border? A $4.6 billion emergency border aid package bill that is needed to keep the humanitarian crisis at the border from worsening was passed by the Democratic-led House on Tuesday.
The passage of the bill set up a showdown with the Republican-led Senate, which passed a broadly bipartisan bill. The White House has threatened to veto the House bill, and it is only reluctantly backing the Senate bill.
In a letter Monday threatening the veto, White House officials complained, among other things, that the bill had no money to toughen border security, including funds for building Trump’s proposed border wall.
‘‘I’m not happy with it because there’s no money for protection,’’ the Republican president said in an interview Wednesday on Fox Business Network. ‘‘It’s like we’re running hospitals now.’’
Material from Globe wire services was used in this report.