A mother who lost her two children to fentanyl poisoning tore into lawmakers in emotionally-charged testimony at a House hearing on the ongoing crisis at the southern border on Tuesday -- telling members of Congress that they need to do more to combat the opioid epidemic.

Rebecca Kiessling, who lost her sons Caleb and Kyler in 2020 to fentanyl overdoses, said that she had been told that the drug which killed them came across the southern border.

Fentanyl, which can be fatal in tiny doses, has been at the epicenter of the U.S. opioid crisis. Officials have said that of the 108,000 overdose deaths in 2021, more than 80,000 were linked with opioids like fentanyl -- which is often cut into other drugs, so people don't know that the drugs they are taking contain it.

Fentanyl is primarily made in Mexico using Chinese precursors and smuggled across the land border. Primarily it is intercepted through ports of entry by CBP’s Office of Field Operations (OFO) as smugglers attempt to bring it to the country in their vehicles, but it is also sometimes stopped by Border Patrol agents in the field.

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Democrats have pointed to increased seizures under the Biden administration at the ports of entry as a sign that attempts to stop the drug are working. But Republicans have warned that an "open" and overwhelmed border is allowing the drug to pour in.

Kiessling noted that tens of thousands of Americans die each year and yet it doesn't receive as much coverage as other events, including the recent Chinese balloon which was allowed to drift over the continental U.S.

"We have a weather balloon from China going across our country, no one died and everyone’s freaking out about it, but 100,000 die every year and nothing’s been done, not enough is being done. Numbers are going up not down."

Rebecca Kiessling fentanyl

Feb 28, 2023: Rebecca Kiessling testifies to Congress on the fentanyl epidemic.

She also pushed back against talk from some politicians who continue to highlight the separation of migrant minors from their parents during the Trump administration.

"And you talk about children being taken away from their parents? My children were taken away from me. 100,000 Americans every year are having their children, 200,000 because it’s both parents, are having their children taken away from them."

Kiessling also accused politicians who of failing to do enough to protect American children, and instead accused them of protecting drug dealers who are evading Border Patrol and getting into the U.S.

"You talk about welcoming those crossing our border seeking protection, you're welcoming drug dealers across our border, you're giving them protection, you're not protecting our children," she said.

She spoke about how some parents of children who have died to fentanyl put purple chairs out in memory of their children, and said it was politicians and the White House that needed that symbol.

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"I don't need a purple chair in my house. Congress needs a purple chair, the White House needs a purple chair to never forget about all those being slaughtered," she said.

"This is a war, act like it! Do something."

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Earlier in the hearing, Republican Chairman Mark Green sought to pin the border crisis as a whole on Homeland Security Secretary Alejandro Mayorkas.

"The Mayorkas border crisis is enriching cartels and human traffickers. Violent cartel and gang activity is significantly increasing throughout the United States, and illegal drugs continue to pour over the border in massive quantities," he said.

Democrats, however, said they were focused on "facts" and finding solutions to the crisis.

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"The fact is Democrats are focused in investing on border staffing, infrastructure, and technology -- especially at ports of entry where the vast majority of fentanyl is trafficked," Ranking Member Bennie Thompson said. "Over 90% of fentanyl seizures take place at our ports of entry or border checkpoints and those responsible are overwhelmingly American citizens, not immigrants."

Fox News' Emily Robertson contributed to this report.