Facebook CEO Mark Zuckerberg faced tough questions from congressional leaders Tuesday, Sen. Amy Klobuchar, D-Minn., among them.

Zuckerberg's appearance on Capitol Hill comes after news that Cambridge Analytica, a political research firm, was able to obtain the personal information of tens of millions of users, leading to intense concerns over user privacy. Those concerns are part of broader questions about the role social media played in Russian interference in the 2016 election.

Wednesday's hearing took place before a joint session of the Senate Judiciary and Commerce committees. Leaders pressed him on a range of items, including Facebook's revenue, treatment of media content and response to Russian meddling.

Klobuchar's first statement to Zuckerberg framed the issue of user data in terms of a burglary. Though Cambridge Analytica may not have forced its way past Facebook's security measures, "it's just like if the manager gave them the keys or they didn't have any locks on the doors," she said. "It's still a breach. It's still a break-in."

Klobuchar followed up with questions that drew potential connections between the data breach and the results of the 2016 election, wondering if Facebook knew if those users with compromised data were concentrated in any specific areas. Zuckerberg said he didn't "have that information with me," but could follow up.

"OK," she said. "Because as we know, the election was close, and it was only thousands of votes in certain states."

Klobuchar also discussed proposed regulations with the Facebook chief, including a bill she helped introduce that would subject those behind online political advertisements to the same disclosure rules as print or television ads. She asked for and received Zuckerberg's acknowledgement that he would support the bill.

Zuckerberg's answers will continue into a second day. Rep. Kevin Cramer, R-N.D., sits on the House Energy and Commerce Committee, will question the social media head Wednesday morning. Cramer said he'd like to ask how Facebook's revenue model would be affected if it weren't able to use personal data to guide advertising. He said he's keeping concern for "free enterprise" in mind as he approaches the hearing, but also recognizes that Facebook, privy to troves of personal data, may be regulated.

And it appears that calls for Facebook to face some type of regulation — be it privacy laws or mandates that users be informed of a data breach — will only grow louder.

"Not only should you be able to have some rules of the road for how you can protect your data," Klobuchar told MSNBC in a Tuesday interview, "You also have, if there's a breach, some rules."