5.45pm: Representatives continue to question Mark Zuckerberg, with one saying that "a devil's bargain has been struck" where Facebook has "evolved to a place where it is gathering data on everyone".
Other questions which have arose so far covered the topics of advertising, security and illegal drug selling on the platform.
Representative Adam Kinzinger showed Mr Zuckerberg a fake account using his name and photograph, but which "isn't anything like me at all".
The account is using his pictures but extorting people for money, he said.
"Fake accounts overall are a big issue because that's how a lot of the other issues around fake news and foreign elections are happening as well," responded Mr Zuckerberg.
Representative David McKinley asked Mr Zuckerberg whether he thinks people should be able to buy drugs on his platform.
Mr Zuckerberg pointed out that such behaviour goes against the site's terms and conditions, but Mr McKinley presented photographs of opioids available to buy on Facebook without a subscription.
"Your platform is still being used to circumvent the law," and allow people to sell drugs, he said, adding: "Facebook is enabling an illegal activity and in so doing you are hurting people."
Growing increasingly animated, Mr McKinley said the adverts of drugs he presented are still active on Facebook.
"You said before you were going to take down those ads, but you didn't do it," he said.
Mr Zuckerberg repeated his belief that artificial intelligence is needed to help police activity on Facebook.
He had earlier mentioned terrorist content as an area in which artificial intelligence allows Facebook to "take down 99% of al Qaida and Isis content" before it is reported by users.
Earlier: Facebook chief Mark Zuckerbeg has begun answering questions on day two of his testimony before Senate committees in Washington.
Mr Zuckerberg said that his own personal data was included in the breach and was shared with third parties.
He also said that it is "inevitable" that there will need to be some sort of regulation of his industry.
"My position is not that there should be no regulation, but I also think you have to be careful about what regulation you put in place," he added.
Mr Zuckerberg began his testamony by apologising again for failing to take a "broad enough view of our responsibility" after the personal details of 87 million users were shared with consultancy firm Cambridge Analytica.
He said in his opening statement: "My top priority has always been our social mission of connecting people, building community and bringing the world closer together. Advertisers and developers will never take priority over that as long as I'm running Facebook."
Yesterday, Mr Zuckerberg admitted the misuse of users' data was a "big mistake" and took personal responsibility for the scandal.
- Digital Desk and Press Association