The Trump administration has taken big steps to solve the border surge of illegal immigrants from Central America, but smuggling cartels are responding by recruiting new migrants from Brazil and Mexico, officials said Tuesday.

The surge peaked in May, with more than 144,000 people nabbed at the Southwest border in that month alone, and has dropped steadily since then, to about 53,000 in September.

Still, agents arrested more than 850,000 illegal immigrants trying to sneak across the border in fiscal 2019, and officers processed about 126,000 more who showed up at ports of entry without papers but demanded entry.

SEE ALSO: Trump admin’s ‘Remain in Mexico’ plan causes tens of thousands to abandon asylum

More than 150,000 are known to have evaded border authorities and made it in — and that’s likely a “conservative” estimate, with the actual tally even higher, acting Customs and Border Protection Commissioner Mark Morgan said.

Standing in front of a section of border wall in El Paso, Texas, Mr. Morgan declared success — but said the numbers are still at a crisis level.

“These are numbers that no immigration system in the world can handle,” he said in El Paso, one of the key flash points for the border surge.

SEE ALSO: More than 150K illegals sneak into U.S. in 2019 during record surge

Combined with those caught beyond the southwest border, more than 1.1 million people were nabbed by agents and officers, Mr. Morgan said. That’s bigger than the populations of U.S. cities such as Austin and San Jose, Calif.

CBP also seized more than 100,000 pounds of cocaine, nearly 2,800 pounds of deadly synthetic opioid fentanyl, and nearly 3,000 illegal weapons — each of those an increase compared to 2018.

Mr. Morgan said that was all the more impressive because it came amid the disruptions of the border surge, when as many as 40% of Border Patrol agents were pulled off the line to perform babysitting duties such as driving and feeding illegal immigrant families and children.

Mr. Morgan said President Trump’s wall-building campaign kicked into gear in 2019, with 76 miles of replacement fence now done, another 156 miles under construction — including some newly fenced areas — and 276 miles in “preconstruction.”

The flow of people across the border now is dramatically different than earlier this year.

Some migrants who earlier may have jumped the border illegally, confident of exploiting loopholes to gain a foothold in the U.S., are now showing up at ports of entry to make claims of admission — a process that is legal.

More than one in five unauthorized border crossers came to the port of entry last month, compared to less than 8% in May, the record month for illegal family migration.

An increasing percentage of those crossers are Mexican families, and agents also are seeing more Brazilians attempting to enter without authorization, Mr. Morgan said.

“I always say this kind of tongue-in-cheek, but I’m serious, that the Mexican cartels and the human smuggling organizations really should teach a business class at Harvard,” he said. “Every single time we attack the current tactics … they change and develop new ones.”

In this case, he said, that means the cartels who just months ago were advertising in Central America, draining some regions of nearly 3% of their population as they headed north, are now running similar ads in Mexico.

Yet even as Mexican cartels create new challenges, Mexico’s government has been instrumental in helping curb the surge of Central Americans who fueled the border crisis.

One critical bit of help has come from the Trump administration’s “Remain in Mexico” policy, which takes would-be asylum seekers from other countries who cross Mexico en route to the U.S. Under the policy, begun in January, many of those people can now be pushed back across the border and made to wait in Mexico while their asylum claims are judged.

The Department of Homeland Security says the Migration Protection Protocols, as the program is officially known, has been a singular success.

Of the 55,000 migrants subject to MPP, only a “small subset” have won their cases and been readmitted to the U.S. to proceed with asylum claims.

Another 20,000 are still waiting in northern Mexico, Homeland Security officials believe. But that leaves tens of thousands who are believed to have given up their claims.

Just as important are the would-be migrants who have not made the trip in the first place, Homeland Security said, cutting the number of illegal immigrant families nabbed at the U.S.-Mexico border by 80% from its record high in May.

The program is also more fair to the migrants, acting Homeland Security Secretary Kevin McAleenan said, since they can get a final hearing and learn their fate within a few months, rather than the years-long backlog for those stuck in the U.S. immigration courts.

The MPP, which began in a few select locations on the border, expanded this week to Eagle Pass, Texas.

“We have already seen individuals granted asylum, and many more fraudulent or non-meritorious cases closed,” Mr. McAleenan said.

Under the old system, asylum-seekers had been allowed to enter the U.S. and roamed free, with few of them returning to be deported when the time came.

Now they are denied that foothold and allowed entry only after they pass the first asylum hurdles.

The theory behind the program is that if someone from a country other than Mexico travels through Mexico, they could claim asylum there, and their continued journey to the U.S. suggests they are regular illegal immigrants seeking jobs or to reunite with families. Neither of those is considered a reason for asylum under the law.

MPP has drawn fierce criticism from immigrant-rights activists who say the policy has created dangerous conditions in northern Mexico, with migrant camps making easy prey for criminals.

Activists have filed several lawsuits, drawing federal judges into the fray, and they are scrutinizing the policy.

Several judges have indicated the policy may need to have more protections for those who, despite coming from other countries, fear being left in Mexico.