After visiting the U.S.-Mexico border Monday with a group of her Democratic colleagues, Congresswoman Nanette Barragán, D-California, said she witnessed a crisis brewing along the frontier. But she said it's not the type of crisis President Trump has been citing to continue demanding billions of dollars for a "steel barrier" and to justify a potential national emergency proclamation.

"I have no doubt that this is part of a greater scheme to try to get this wall built and making it seem like it's a national security crisis — and it's not," Barragán told CBS News.

The California Democrat said the crisis at the border is a humanitarian one created by the president's hardline immigration agenda. She underscored the December deaths of Jakelin Caal and Felipe Alonzo Gomez, two migrant children from Guatemala who were in Border Patrol custody, and what she said were poor conditions in some of the migrant holding facilities along the border.

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"The numbers the administration has been putting out are misleading the public," Barragán said. "I can tell you that I have not heard in briefings, as a member of the Homeland Security Committee, what we're hearing publicly now."

In recent days, the Trump administration has been citing national security concerns to defend its unwavering request for $5.7 billion in funds to construct a barrier along the southwestern border. And as Democrats have stood firm on their opposition to the White House's request, the president has repeatedly floated the idea of circumventing Congress and proclaiming a national emergency to use Department of Defense funding to erect a border barrier — a move some lawmakers have said would likely be challenged in court.

On Monday, White House director of strategic communications Mercedes Schlapp told reporters, "We have a crisis on the border" when asked about the status of budget negotiations to end the prolonged government shutdown — now the second-longest in U.S. history. Later in the day, the president tweeted he will deliver a prime-time address to the nation Tuesday night to discuss a "Humanitarian and National Security crisis." Mr. Trump will also travel to the southern border Thursday.

To make a case for border wall funding during an appearance on "Fox News Sunday," White House press secretary Sarah Sanders repeated a false claim she made Friday that Customs and Border Protection (CBP) picked up nearly 4,000 known or suspected terrorists last year "that came across our southern border."

In a statement Monday night, the Department of Homeland Security (DHS) said authorities prevented more than 3,700 individuals on the terrorist watchlist from entering the U.S. in fiscal year 2017. But the agency conceded most of these individuals tried to enter the country through airports. And a report released by the State Department in September mentioned "no credible evidence" exists of terrorists entering the U.S. by crossing the border with Mexico.

Similarly, DHS secretary Kirstjen Nielsen said last week CBP stopped over 3,000 "special-interest aliens" who attempted to cross into the country illegally through the southern border.

According to DHS, the "special-interest aliens" Nielsen cited are foreign nationals whom the government believes have travel patterns that "possibly have a nexus to terrorism." In Monday's statement, the agency said not all "special-interest aliens" are terrorists.

When pressed about the statistic Monday by reporters, Nielsen said it was classified. "What we can say is that we absolutely have had cases of terrorists crossing the southern border. The number itself is sensitive and that's why it's difficult, it's classified for obvious reasons, ongoing investigations," Nielsen said during a press briefing with Vice President Mike Pence. "But we can also say there are thousands literally thousands of known or suspected terrorists traveling throughout the hemisphere."

"One terrorist is too many," she added.

Barragán, a member of the House Committee on Homeland Security, said the information she has received from committee reports and from her visit to border areas in New Mexico and Texas differs from the figures the White House has been disseminating. "We're hearing one thing from rank and file officers and another thing from management," she said. "And that raises a huge red flag."

The Los Angeles area legislator said House Democrats will use their new investigative powers over the Trump administration to scrutinize its statistics on migrants coming to the southwestern border — as well as Jakelin and Felipe's deaths.

"It appears to me that the American people are being misled," Barragán said. "And that is why Congress needs to provide the oversight. That's why we do these trips — to get the answers."