Melania Trump
Melania Trump

U.S. first lady Melania Trump returned Thursday to the country's border with Mexico, her second visit in a week to get a firsthand look at conditions surrounding the detention of thousands of migrants who have illegally entered the country, including children separated from their parents.

Melania Trump landed at an air base in Arizona along the southwestern border with Mexico and visited a U.S. Customs and Border Protection facility. She engaged in a roundtable discussion with border and immigration officials, the U.S. Marshals Service and a local rancher to get their thoughts on the influx of migrants into the U.S. Last week, she visited with immigration authorities further to the east in Texas.

WATCH: Melania Trump Arrives in Arizona for Border Visit

President Donald Trump and his administration are confronting an immigration crisis, the result of his "zero tolerance" policy aimed at apprehending anyone who illegally crosses the Mexican border into the U.S. For weeks, U.S. agents separated children from their parents, sending the youths to shelters in far-flung states and detaining their parents while they waited for legal proceedings on their asylum claims to stay in the United States.

But Trump, faced with an outcry in the U.S. and from around the world about the voices and pictures of the children as they were split from their parents, last week reversed the policy and ordered that the families be kept together. It was Trump's biggest policy reversal in his 17-month presidency.

The U.S. now has custody of about 2,000 children who were separated from their parents. A federal judge has ordered that the youngest ones under five years of age be reunited with their parents in the next two weeks, and older children within a month.

Melvin Garcia, 37, a deportee from the U.S. who wa
Melvin Garcia, 37, a deportee from the U.S. who was separated from his daughter Daylin Garcia, 12, shows a letter sent by U.S. Immigration and Customs Enforcement during an interview with Reuters in Choloma, Honduras, June 21, 2018. The letter reads "Your daughter is detained in a juvenile detention center in South Texas. She is pending an appointment in court.”

On Thursday's border visit, Melania Trump was told by one official that since last October 1,100 unaccompanied children have crossed the border into Arizona.

“Look at these photographs in front of you, Mrs. Trump, so you can see this six-year-old boy was left in the desert out near Lukeville, Arizona," one customs and border official said. "You can see that he has a Coke bottle. You can see he has a note in his hand. We actually did a press release on this because people also have to understand the dangers of the desert, of the heat, of the violence, that exists out there. So, this is something our people encounter on a daily basis, seeing children out there ... and families in very dangerous situations.”

"It’s incredible," she said, "as young as six years old, somebody would leave him. Wow. Very sad."

The first lady was widely mocked last week for leaving and returning to Washington wearing a jacket with lettering on the back saying, "I really don't care. Do U?" a message that left many Americans puzzled about her intent.

First lady Melania Trump arrives at Andrews Air Fo
First lady Melania Trump arrives at Andrews Air Force Base, Maryland, June 21, 2018, after visiting the Upbring New Hope Children Center in McAllen, Texas. The first lady's team insisted that there was no hidden meaning behind the wording on the back of her jacket.

But on Thursday, she wore an unadorned black pullover shirt and white pants.

Melania Trump's spokeswoman, Stephanie Grisham, said the first lady continues to discuss the plight of the immigrant children with her husband, who encouraged her to make the Arizona trip.

"This is a complex issue," Grisham said. "She recognizes that. She's advocating for quality care for these children under difficult circumstances."

"She cares about children deeply,” the spokeswoman said. “She also believes in strong border laws and treating everybody equally.”