WASHINGTON – Department of Homeland Security Secretary Kirstjen Nielsen on Saturday called on federal courts to enforce existing immigration laws to stem the tide of undocumented migrant families from entering the United States and Congress to fix a broken immigration system that has created “a humanitarian crisis” at the southern border.

“The system is clearly overwhelmed and we must work together to address this humanitarian crisis and protect vulnerable populations,” Nielsen said in a statement released Saturday after her meetings Friday with local and federal officials in El Paso, Texas, one of the nation’s busiest border crossing points. “We know that if Congress were to act, or the courts were to enforce the law as written, we could address this crisis tomorrow. Instead we continue to do more with less.

“As I have said before, I ask Congress to please put politics aside and recognize this for the growing security and humanitarian crisis it is,” said Nielsen, who is visiting border facilities in Yuma, Arizona, on Saturday.

Nielsen arrived in El Paso Friday following the deaths this month of two migrant children who were in Customs and Border Protection custody. She met with officials there in response to the increase in the apprehensions of families and unaccompanied children crossing the border illegally, including those with illnesses.

This week, Nielsen ordered a series of actions to care for undocumented immigrants who are apprehended, including U.S. Customs and Border Protection medical exams for all children it holds in custody. United States Coast Guard medical personnel deployed to the border to assist the Border Patrol in health screenings.

In a Saturday tweet, President Donald Trump blamed the deaths on Democrats "and their pathetic immigration policies that allow people to make the long trek thinking they can enter our country illegally."

"If we had a Wall, they wouldn’t even try!," he tweeted in a reference to the border wall he's seeking that has led to the federal government's partial shutdown, now in its second week.

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Rep. Joaquin Castro, D-Texas, has said many questions remain unanswered regarding the deaths, but noted the "lack of adequate medical supplies, equipment and resources" at CBP detention facilities to treat migrants and the agents working there.

Castro also suggested that many more migrants were taking more dangerous paths into the country because of the Trump administration's policy of turning asylum-seekers away from legal ports of entry. This policy, he said, was "putting families and children in great danger."

The administration has struggled to deal with an unprecedented influx of family units and unaccompanied minors along the southern border, many claiming asylum.

That spurred last spring’s controversial "zero-tolerance" policy that resulted in thousands of separated families. It was later blocked by a federal judge.

In the past two months, two other federal judges have ruled against actions by the Trump administration to deal with the migration crisis.

The court decisions come at a time, say DHS officials, when the number of immigrant families and unaccompanied children has risen dramatically. CBP apprehensions in those categories rose 86 percent – more than 68,000 family units and almost 14,000 unaccompanied children – over last year’s total.

At a contentious congressionalhearing Dec. 20, Nielsen and Democratic lawmakers got into a heated exchange over administration policies to resolve the border crisis.

Nielsen repeatedly defended her department's actions, saying her agents are dealing with an unprecedented wave of asylum-seekers that has overwhelmed the U.S. immigration system and requires massive changes in U.S. immigration law.

She told the House Judiciary Committee that Customs and Border Protection needs more officers to man the nation's ports of entry, that Border Patrol needs more agents to patrol regions in between, and that the southern border will never be completely secure until the U.S. completes a "wall system" including a combination of walls, fencing, and technology.

And she repeatedly asked the members to update U.S. laws that allow unaccompanied minors and family units to apply for asylum and remain free in the country.

“This crisis is the direct result of loopholes created by federal law and adverse federal court rulings that prevent the detention and repatriation of illegal unaccompanied alien children and family units,” she said.

Republican El Paso Mayor Dee Margo, who met with Nielsen during her visit Friday to the border city, told the El Paso Times that the DHS chief is correct in blaming the border crisis on Congress.

“If I’m going to blame somebody, I’m not going to blame CBP. They’re just trying to follow law enforcement requirements,” he said. “I’m blaming Congress on both aisles, in both houses, because they’ve had plenty of opportunities to deal with this but they haven’t had the fortitude to do it and it’s time they man up.”

“That’s my frustration. I can’t blame people for dealing with a system that’s broken, doing the best they can. They need to fix the system,” he added.

On Saturday, in response to what he called Nielsen’s “latest photo opportunity” in Yuma, Rep. Raul Grijalva, D-Arizona, again called on her to step down from DHS.

“I’ve been clear from the beginning,” he said in a statement. “Secretary Nielsen has no business serving as DHS Secretary, and the latest accountability and transparency issues at DHS provide more evidence that she is unfit to lead. I reiterate my call for her to resign.”

Contributing: Eliza Collins, Sergio Bustos and El Paso Times