After whistleblower Frances Haugen raised concerns around Facebook's resourcing of counterterrorism and teams intended to counter foreign influence, lawmakers opened the door to holding another hearing. 

"I believe Facebook's consistent understaffing of the counterespionage, information operations and counterterrorism teams is a national security issue, and I'm speaking to other parts of Congress about that," Haugen said.

Sen. Dan, Sullivan, R-Alaska, followed up, "So you're saying in essence that the platform, whether Facebook knows it or not, is being utilized by some of our adversaries in a way that helps push and promote their interests at the expense of America's?"

"Yes," she replied. "Facebook is very aware that this is happening on the platform, and I believe the fact that Congress doesn't get a report of exactly how many people are working on these things internally is unacceptable because you have a right to keep the American people safe."

“I have strong national security concerns about how Facebook operates today,” she added.

Sen. Richard Blumenthal, D-Conn., then raised the possibility of holding a second hearing with Haugen on the issue and went on to thank her for her bravery and called for other whistleblowers to come forward.

Facebook said communications staffer Andy Stone would live-tweet through the Senate hearing to respond to Frances Haugen's testimony.

"Just pointing out the fact that @FrancesHaugen did not work on child safety or Instagram or research these issues and has no direct knowledge of the topic from her work at Facebook," he tweeted. "As she herself just said under oath, 'I don't work on it.'"

Sen. Amy Klobuchar, D-Minn., had asked if teenagers are some of Facebook's most profitable users.

"I'm sure they are some of the more profitable users on Facebook, but I do not work directly on them," Haugen said.

Facebook also pointed to a May op-ed in CNBC from Nick Clegg, Facebook vice president of global affairs, calling for "bipartisan approach on internet regulation."

But lawmakers from both parties on Tuesday, in a normally divided Washington, were united in blasting the social media giant after they said internal documents Haugen presented to them showed Facebook ignored its own evidence that it harms young users and fuels hate speech. Haugen also alleged CEO Mark Zuckerberg had the opportunity to intervene but dismissed the concern.

Using Ethiopia as an example, Facebook whistleblower Frances Haugen told lawmakers the company is "pulling families apart" and fueling "ethnic tensions" as the platform's news feed ranking algorithm, via "meaningful social interactions" or MSIs, elevates polarizing content.

She said she has submitted documents to Congress showing Facebook CEO Mark Zuckerberg was presented with "soft intervention options" to MSIs in April 2021 and chose not to add features to intervene.

"Facebook's own algorithms are bad at finding this content. It's still in the raw form for 80, 90% of even that sensitive content," she said. "In countries where they don't have integrity systems in the language local language, and in the case of Ethiopia, there are 100 million people in Ethiopia and six languages -- Facebook only supports two of those languages for integrity systems."

“This strategy of focusing on language-specific content-specific systems AI to save us, is doomed to fail," she added. 

Asked why Facebook wouldn’t get rid of "downstream MSIs" when data showed the system expanded hate speech, misinformation and violence-inciting content, she claimed that employee bonuses are still currently tied to MSIs.

"If you hurt MSI, a bunch of people weren't gonna get their bonuses," she said.

With the mental health of teens and preteens a prime focus at Tuesday's hearing, Sen. Amy Klobuchar, D-Minn., asked Haugen directly if Facebook hooks users to its platforms at a young age in order to make them more profitable over the long term.

"They know that children bring their parents online -- so they understand the value of younger users for the long-term success of Facebook," said Haugen.  

She also said they know children will bring family members to the platform, if not the reverse. 

"Facebook understands that if they want to continue to grow they have to find new users. They have to make sure that the next generation is just as engaged with Instagram as the current one, and the way they'll do that, making sure children establish habits before they have good self-regulation," added Hagen.

"By hooking kids?" asked Sen. Brian Schatz, D-Hawaii. 

"By hooking kids," Haugen affirmed. "We need to protect the kids."

-ABC News' Zunaira Zaki, Mary Kathryn Burke and Victor Ordonez