The latest data suggests that recent measures to crack down on illegal immigration have not deterred migrants, many of whom make the arduous journey over land from Central America to escape gangs and drug cartels, though others come in search of better jobs and education opportunities.

Some immigration experts argue that the asylum system in the United States is being abused by applicants who are seeking to move to the country primarily for economic reasons. But scholars who have examined the system closely say that the flow of asylum seekers from certain regions, especially the northern triangle of Central America, comprised of El Salvador, Guatemala and Honduras, reflects widespread human rights abuses in those countries.

“You always have to be careful of fraud, but having some economic motives for requesting asylum shouldn’t necessarily be disqualifying,” said Jaya Ramji-Nogales, a law professor at Temple University. “Widespread violence in some countries contributes to dire economic problems. Most people applying for asylum are fleeing a desperate situation.”

The Trump administration in recent months deployed thousands of National Guard troops to the border, and on May 7 introduced a “zero-tolerance” policy that calls for prosecuting everyone who illegally enters the country.

Those who petition for asylum at official crossings like the one in Nogales are not considered illegal border-crossers, and are not prosecuted under that policy, yet their numbers are also so substantial that the Trump administration is struggling to control the influx.

Under current law, people who claim fear of persecution in their home countries are entitled to what is known as a credible fear interview. If they show a “significant possibility” of winning their asylum case, they are usually admitted into the United States to await a court hearing before a judge who decides their case.

Their cases join a ballooning backlog in the immigration courts, 700,000 in total, meaning they could take years to be decided, even though the Justice Department recently said it would set completion targets for judges.