HOUSTON — While the Trump administration focuses attention on migrant caravans trying to cross the southern U.S. border in California, migration is surging at the opposite end of the border in South Texas.

Last weekend in the Rio Grande Valley, Border Patrol agents caught 1,900 people trying to cross the southern border illegally.

Border agents in the Rio Grande Valley are apprehending around 680 people a day, compared to up to 145 arrests daily in San Diego, across the border from Tijuana, Mexico, where an estimated 6,000 people are waiting to cross.

Raul Ortiz, the Border Patrol's acting chief for the Rio Grande Valley, said about a dozen people have claimed to have been part of a migrant caravan.

About 380 people per day are adults with children, which the Border Patrol categorizes as "family units." About 75 unaccompanied minors are caught daily. They primarily come from Guatemala or Honduras, countries wracked by gang violence and poverty.

The Border Patrol apprehended more 50,000 people on the southern border in October, the highest monthly number this year. Ortiz said migrant traffic has remained largely consistent through November.

Many migrants are brought to the Rio Grande Valley, the busiest corridor for illegal crossings, by human smugglers known as "coyotes" who charge thousands of dollars per head.

About 2,600 soldiers were sent to South Texas by President Donald Trump , who ordered an active-duty military deployment in response to the caravans. The soldiers set up camp near the border crossing at Donna and laid razor wire near several of the bridges spanning the Rio Grande, the river separating the U.S. and Mexico.

Soldiers have remained in Texas even though the caravans headed west. Ortiz said the deployment and a previous National Guard mission had helped free up Border Patrol agents to apprehend migrants.

But drug seizures have fallen slightly in the Rio Grande Valley, Ortiz said. Part of the reason why, he said, is "the amount of energy (the Border Patrol is) having to spend" on detaining large numbers of migrants.

The unabated wave of migration has also led to surging numbers of adults and children being detained. A temporary detention facility for children in Tornillo has continued to expand, with signs that the facility is becoming more permanent .

Sister Norma Pimentel, executive director of Catholic Charities of the Rio Grande Valley, said the shelter she supervises is taking in 100 to 200 families daily.

"People are coming in great numbers, and they haven't stopped," she said.

Pimentel said she once asked a group of migrants why they continued to risk the journey knowing how difficult it would be to stay in the U.S. once they arrived.

"They said, 'I have to come because it's worse if I stay home. It's more dangerous,'" she said.