BROWNSVILLE, Texas >> Paying a smuggler, Edgar Mejia could afford to take only one child with him to the United States. He chose his 3-year-old “warrior” son, leaving his 7- and 12-year-olds with their mother in Honduras.

“Pitifully, I had use him like a passport to get here,” Mejia said last week after picking up milk from volunteers at a Brownsville, Texas, bus station for the last leg of their journey to join relatives in Atlanta. “I am here because of him.”

Mejia, 32, and his son, who paid a smuggler $6,000 for a “new dream” that Honduras couldn’t provide, are among the Border Patrol’s nearly 170,000 encounters with migrants on the U.S.-Mexico border in March, a 20-year high. The total, announced Thursday, includes nearly 19,000 children traveling alone, the highest monthly number on record.

About four in 10 border encounters last month were with families and unaccompanied children — many from Guatemala, Honduras and El Salvador — at a time when policies in the U.S. and Mexico favor them staying in the United States while they seek asylum. It marks the third sharp jump in Central American asylum-seekers in seven years.

For decades, predominantly Mexican men crossed the border illegally, with many returning for visits until heightened border security made going back and forth more difficult. Migration rose and fell but was fairly steady and predictable.

Over the last decade, a complex mix of factors has produced periodic, dramatic spikes, especially among families and children, who get more legal protections and require more care. The Government Accountability Office identified 10 potential causes for a spike in the number of unaccompanied children at the border in 2014, including poverty, violence and perceptions of U.S. immigration policy.

A large increase in family arrivals in 2019 followed an end to the Trump administration’s practice of generally separating parents from their children at the border. The latest jump follows ferocious storms in Central America and President Joe Biden ending his predecessor’s hardline immigration policies, though many changes attributed to Biden are rumors or have been fabricated by smugglers to generate business.

The “root causes” prompting Central Americans to leave haven’t changed, said Sister Norma Pimentel, executive director of Catholic Charities of the Rio Grande Valley in Texas, whose temporary shelter has been hosting 400 to 500 people nightly, compared with a peak of about 1,000 in 2019.

“I think that it’s simply that the traffickers use whatever is happening in the United States to extort the families, to lure them, to create a narrative that says, ‘Come right now. The president is going to let you in,’” she said.

Migrants, in dozens of interviews over the last two weeks, generally said circumstances in Central America led them to the U.S. When asked about Biden, nearly all said his relatively pro-immigration positions influenced their thinking.

Smuggling fees vary widely, with some paying up to $10,000 a person in the Rio Grande Valley, the busiest corridor for illegal crossings. There is often a discount for additional relatives. The trip can take weeks in cars, buses and trucks, ending when an inflatable raft reaches the banks of the Rio Grande and families and children turn themselves in to Border Patrol agents.

Mejia said he and his son were in a group of 18 Hondurans on a trip divided into four parts, including one leg traveling in a trailer from Mexico City to Monterrey and a final stretch in an open-top boxcar to the border city of Reynosa. Children were told to be quiet when the trailer came to military checkpoints.

“(Smugglers) tell you it’s going to go well, but the reality is different,” Mejia said, turning to his 3-year-old son at the bus station in Brownsville, a border city of about 200,000 people on the Rio Grande. “I have a warrior here. We suffered greatly.”

Douglas Perez, 24, said he stood with 10 people in a covered pickup truck, including his wife and two children, ages 4 and 1. He held the baby, planting his palm on the roof to avoid falling over. They were released in the U.S. with notices to report to a U.S. Immigration and Customs Enforcement office.

Perez, who paid a smuggler $27,000 to bring his family to the U.S., said he left the western highlands of Guatemala because his job picking corn no longer provided enough food to eat.

Carlos Enrique Linga, who was released from custody with his 5-year-old daughter, said he could no longer afford new clothes for his family in Guatemala after rains destroyed their house. That prompted him to try to join a friend in Tennessee to earn money. His wife, 2-year-old twins and newborn stayed in Guatemala because they couldn’t pay a smuggler.

“Our houses got carried away by the current, the water,” Linga said after breakfast in a migrant shelter in Mission, Texas. “Our ranch is no more. We are without a house.”

The Border Patrol had 168,195 encounters with migrants last month, the highest since March 2001. The numbers aren’t directly comparable because more than half of those stopped last month had been quickly expelled from the country under federal pandemic-related powers that deny people the right to seek asylum. Being expelled carries no legal consequences, so many people make multiple attempts.

Biden has exempted unaccompanied children from expulsion, allowing them to stay in the U.S. while pursuing asylum claims and live with “sponsors,” usually parents or close relatives.

Mexico has been reluctant to take back Central American families with young children, especially in Tamaulipas state bordering the Rio Grande Valley, so many of them are being released in the U.S. while their claims are considered by immigration authorities.

Migrants who enter the Rio Grande Valley as single adults or in families with children 7 and older are expelled to Reynosa, an organized-crime stronghold. Unfounded rumors are rampant in a plaza there where migrants plan their next move. Last week, rumors spread that the U.S. would open its borders April 5 or that the borders would be open for Biden’s first 100 days in office.

Hermelindo Ak, a corn grower, heard in Guatemala that chances were better for families but didn’t know how a child’s age was considered. Information seemed to change “day to day,” he said.

He was expelled with his 17-year-old son, then sent his son alone for a second attempt after learning unaccompanied children can stay in the U.S. Ak, 40, planned to return home to his wife and other children, who stayed in Guatemala because they couldn’t afford to pay a smuggler.