WASHINGTON (WASHINGTON POST) - Homeland Security Secretary Kirstjen Nielsen is considering a series of measures to halt a new surge of Central American families and unaccompanied minors coming across the Mexican border, including a proposal to separate parents from their children, according to Trump administration officials with knowledge of the plans.

These measures, described on condition of anonymity because they have not been publicly disclosed, would also crack down on migrants already living in the United States illegally who send for their children.

That aspect of the effort would use data collected by the Department of Health and Human Services (HHS) to target parents for deportation after they attempt to regain custody of their kids from government shelters.

The Department of Homeland Security (DHS) has previously considered some of these proposals, but there is renewed urgency within the administration to address an abrupt reversal of what had been a sharp decline in illegal immigration since Mr Trump took office in January.

In November, US agents took into custody 7,018 families, or "family units," along the border with Mexico, a 45 per cent increase over the previous month, the latest DHS statistics show. The number of Unaccompanied Alien Children, or UACs, was up 26 per cent.

Children's shelters operated by the HHS are now at maximum capacity or "dangerously close to it", an official from the agency said.

Overall, the number of migrants detained last month along the Mexico border, 39,006, was the highest monthly total since Mr Donald Trump became president, according to DHS figures.

The proposals were developed by career officials at Immigration and Customs Enforcement (ICE) and other DHS agencies, administration officials said.

Mr Tyler Houlton, a DHS spokesman, confirmed the agency has "reviewed procedural, policy, regulatory and legislative changes", to deter migrants.

Without giving further details, he said some of the measures "have been approved", and DHS is working with other federal agencies "to implement them in the near future".

"The administration is committed to using all legal tools at its disposal to secure our nation's borders and as a result, we are continuing to review additional policy options," Mr Houlton said.

The most contentious proposal - to separate families in detention - would keep adults in federal custody while sending their children to HHS shelters.

This was floated in March by then-Secretary of Homeland Security John Kelly, now the White House Chief of Staff.

He told CNN at the time that the children would be "well cared for as we deal with their parents".

General Kelly did not move forward with the plan, in part because of the backlash it triggered, administration officials said, and also because illegal migration had plunged to historic lows.

Trump administration officials described the measures as an unpalatable but necessarily tough series of policy options to discourage Central American families from embarking on the long, dangerous journey to the border - or hiring smugglers to bring their kids north.

"People aren't going to stop coming unless there are consequences to illegal entry," one DHS official said.

Migrants from El Salvador, Guatemala and Honduras represent the largest share of families and children taken into US custody along the border, with many telling border agents that they fear for their lives if sent back to their home countries.

The three nations, known as the "Northern Triangle" of Central America, are crippled by gang violence and homicide rates that are among the world's highest.

Trump administration officials say Central American migrants and the paid smugglers who bring them to the border shamelessly exploit Americans' compassion, entering the United States illegally and gaming the asylum process.

If a migrant's stated fear of being sent home is considered "credible", they enter an asylum process that may take years to adjudicate, and the flood of such petitions in recent years has worsened the backlog of more than 600,000 cases pending in US immigration courts.

Asylum seekers are typically issued work permits while they wait for the process to play out, and when their rejected appeals are exhausted, they often ignore court orders to leave the United States, choosing to remain in the country illegally.

The Trump administration wants to significantly expand immigration detention capacity, and hire more judges and expedite asylum cases to stop migrants from taking advantage of what they call "loopholes" in the asylum process.

The proposal to separate parents from their children is viewed by the agency as a more immediate tool to halt the latest border surge.

DHS has three family detention centres - two in Texas, one in Pennsylvania - with about 2,200 beds available. But legal restrictions on its ability to detain children mean that families are typically given a court date and released from detention not long after they arrive.

November saw the three detention centres reach their highest occupancy levels for the year, and they remain near maximum capacity, officials said.

"The parents that would undertake this perilous journey to the United States would be less likely to do it if they knew they would be separated from their kids," said Dr Andrew Arthur, a resident fellow at the Centre for Immigration Studies, which seeks to reduce immigration.

A former US immigration judge and Republican congressional policy staffer, he called it "a reasonable step to take".

"It might seem heartless, but it's more heartless to give them the illusion they're going to be able to enter the United States freely by hiring a smuggler to come here, because the dangers associated with smuggling along the south-west border are real," Dr Arthur said.

The unaccompanied minors are typically seeking to reunite with a parent already living illegally in the United States.

By law, migrants under age 18 who arrived without a parent must be turned over to the HHS within 72 hours of being taken into DHS custody. The shelters where they are housed are designed to be more like boarding schools than grim detention centres.

The minors remain in the care of the HHS's Administration for Children and Families (ACF), while another HHS agency, the Office of Refugee Resettlement, seeks to identify an adult sponsor who can take custody of them.

The process takes about six weeks on average, HHS officials say.

"It's a little-known fact that over half of those who enter illegally are placed with a parent already in the United States," said ACF spokesman Kenneth Wolfe.

The parents, or any other adult seeking to take custody of a child, must submit to an extensive background check that includes information about their immigration status.

But administration officials say that information is not checked against DHS biometric data, nor shared with ICE for potential enforcement purposes. The new DHS proposals under consideration would change that.

If children are forcefully separated from their mothers and fathers, or if parents know they could be arrested or targeted for trying to reunite with their kids, migrant advocates say the US government will be inflicting "devastating" trauma on families fleeing Central America because they feel their lives are at risk.

"These measures will only drive families who are vulnerable to exploitation further into the hands of traffickers and smugglers," said Mr Greg Chen, director of government relations at the American Immigration Lawyers Association.

"These are families that have no other choice for their survival," he said.