Washington(CNN) Across Capitol Hill Wednesday, lawmakers grilled several key Trump administration officials over its enforcement of immigration law, including the "zero tolerance" policy that led to the separation of migrant children from their parents at the border last year.
Democrats relentlessly pressed Homeland Security Secretary Kirstjen Nielsen to explain some of President Donald Trump's statements on immigration and his national emergency order. Homeland Security's acting inspector general said the office is investigating how the agency is processing asylum seekers and whether undocumented parents were deported without their children. And Customs and Border Protection Commissioner Kevin McAleenan was forced to rehash the botched rollout of that policy to skeptical lawmakers.
Here are five takeaways from Wednesday:
Nielsen's appearance demonstrated the difficult position administration officials are in. For months, Democrats have expressed their outrage on a slew of immigration policies and they now have the opportunity to confront officials, and in this case, Nielsen, with those concerns.
Some of the most tense exchanges revolved around the "zero tolerance" policy, which called for the criminal prosecution of all adults and as a result, separated children from their parents. Nielsen repeatedly said that the administration was simply enforcing the law and that it was not a policy.
"We enforce the law," she told Rep. Kathleen Rice.
Nielsen later added: "The whole purpose of [the policy] was to increase consequences for those who choose to break the law."
Democratic Rep. Al Green went on to accuse the administration of preventing people of color from coming to the US.
"White babies would not be treated the way these babies of color are being treated, Madam Secretary," he said. "This is about color. We've opened our doors, your tired, your poor, your huddled masses, yearning to breathe free. Except we now have our quota of people of color."
Nearly a year after then-Attorney General Jeff Sessions announced the "zero tolerance" policy, there are still few answers on how the policy came to fruition, who was consulted, and how many people it impacted.
Nielsen, the highest official to testify on the issue this year, said that while she discussed the policy with Sessions, she did not know Sessions was going to announce the policy when he did -- April 6, 2018.
"At some time before the announcement we had the conversation, I did not know he was making that announcement that day," Nielsen said.
Since the policy ended, a series of government reports have revealed the chaos and confusion that ensued when it was rolled out as far back as 2017. A Health and Human Services inspector general report, for example, recently found that thousands more children had been separated than previously acknowledged. The exact figure is uncertain because there wasn't a system to track them.
Another inspector general, Homeland Security acting Inspector General John V. Kelly, told a House appropriations subcommittee there are three ongoing investigations into the administration's immigration enforcement actions. He said one was the result of a major report released in October that found the Department of Homeland Security was "not fully prepared" for the zero-tolerance policy.
Democrats pressed Nielsen to respond to statements Trump had made about the situation along the US-Mexico border, especially in light of his declaring a national emergency.
Nielsen had to maneuver through the hearing, trying not to contradict the President, while at the same time not repeating some of his misleading claims.
Homeland Secretary Committee Chairman Bennie Thompson, who had multiple testy exchanges with the secretary, asked about the President's statement that he "didn't need to" declare a national emergency.
In February, while declaring a national emergency to fund a border wall, Trump said, "I could do the wall over a longer period of time, I didn't need to do this, but I'd rather do it much faster."
Nielsen defended the move, but fell short of providing details on how Trump came to that decision.
"My conversations, of course, with the President, generally speaking, are protected under privilege, but what I would say is his explanation in general, in public has been that he hoped Congress would act, that it didn't have to come to issuing an emergency declaration if Congress had met his request to fund the resources that CBP has requested," said Nielsen.
She was also asked to respond to Trump saying that more people are being caught crossing over the border than ever before.
During a visit to Mission, Texas, in January, Trump said there's never been "so many apprehensions ever in our history."
"Is the President misleading the American people? Is he accurate in what he is saying? It's the largest amount of detentions -- apprehensions at the border?" said Rep. Jim Langevin.
At another point, Langevin asked: "We went from 1.6 million in 2000, apprehensions, (to) 400,000 in 2018. The President said that there were never so many apprehensions at the border in our history up until now. Is that accurate? Was the President accurate?"
Nielsen carefully responded, withholding a direct judgment on Trump's statements and emphasizing increases in some places.
"What I can tell you is that in some places, we have had record months of families, in some areas we have had record numbers of apprehensions," she said.
Nielsen said that the US is on track to apprehend 900,000 undocumented immigrants at the southern border this year.
The last year to reach over a million apprehensions was 2006, with 1,089,092, and 2007 was the next closest with 876,704.
Customs and Border Protection Commissioner Kevin McAleenan told the Senate Judiciary Committee that the administration has stepped up one of its key new efforts to handle the surge of migrants at the border.
The so-called Migrant Protection Protocols, which require some asylum seekers to wait for their immigration court hearings in Mexico, will now also apply to migrants who illegally cross the US border in CBP's San Diego sector, McAleenan said.
Previously, the policy had only applied to some migrants who sought asylum at the San Ysidro port of entry.
"If you cross illegally," he said, "you're still going to have to wait in Mexico for your court proceeding."
The policy, informally known as "Remain in Mexico," is facing a legal challenge and sharp criticism from immigrant advocacy groups, who argue it places vulnerable migrants', most of whom are from Central America, in harm's way.
But as he made the administration's case about what he described as a crisis at the border, McAleenan maintained officials' aim is providing "safe and lawful" access to asylum.
"What it's going to allow us to do is actually increase access to court proceedings and to increase access at ports of entry to process more people, because we don't have to hold them in the limited space available at the port or in ICE facilities," he said.
Nielsen told the House panel that administration's goal is to have all asylum seekers wait in Mexico until they have a court hearing in the US.
"We do it conjunction with them (Mexico) as we expand the program," Nielsen said. "We are doing it in a very systematic way, but the goal is to expand that across the border."
Despite the administration's implementation of numerous policies to stem the flow of migrants and a national emergency declaration, the number of apprehensions are skyrocketing.
Nielsen said the US is on track to apprehend 900,000 migrants at the border this year.
For context, 2006 was the last year to reach over a million apprehensions. And total apprehensions have remained under half a million since 2010.
Nielsen underscored that the difference between illegal immigration today compared to the past is "who is arriving."
Historically, migrants crossing illegally into the US were predominantly single adult males from Mexico, but now more than 60% of migrants are families and unaccompanied alien children, and 60% are non-Mexican, said Nielsen.
In the Senate Judiciary hearing, Democrats emphasized the importance of addressing conditions in Central America.
"You cannot treat emphysema with cough drops. And the notion that we can ignore what's in these three countries and what's causing these people to risk their lives to come to the United States is naïve and wrong," said Sen. Dick Durbin, D-Illinois. "We need to treat both situations, the root causes of this migration to the United States, and the treatment of those who come to the border."
Republican senators offered a different explanation for why the administration's policies haven't led to a drop of migrants approach the border, arguing that it's on Congress to do more.
"All of us ought to hide our heads in a bag," said Sen. John Kennedy, R-Louisiana. "This is unconscionable."