Representatives from Facebook, Twitter and Google faced tough questions from members of the US Congress on Tuesday.

Lawmakers want to better understand how the Russian government may have used these online platforms to try and sway the American presidential election, and what the tech giants are doing about it, reports the CGTN.

US lawmakers want answers from three social media firms. Just what did Facebook, Twitter and YouTube-owner Google, know about Russian involvement in the American political process, and how long have they known about it?

 On Tuesday, Democratic and Republican senators in Washington grilled representatives from the tech giants to see how they were exploited and what the firms have done to stop it.

In the months immediately following the 2016 election, Facebook head Mark Zuckerberg scoffed at the idea that Russian agents used his globally popular site to successfully influence the election.  It took Facebook, and the others, months to launch their own internal investigations. 

This week, Facebook admitted that a Russian-based firm called the Internet Research Agency, which is believed to have ties to the Kremlin, reached 126 million users in the U.S.

Google admitted the same agency uploaded 1,000 videos to YouTube, and Twitter said the group sent 131,000 messages. These numbers are significantly more than any of them had previously admitted.

Representatives from the firms said they are now taking this very seriously.

‘The foreign interference we saw is reprehensible,’ Facebook General Counsel Colin Stretch told Congress said. ‘That foreign actors hiding behind fake accounts abused our platform and other internet services to try to sow division and discord, and to try and undermine the election, is directly contrary to our values and goes against everything Facebook stands for.’

Many Democrats have argued that President Donald Trump won in part because of Russian government interference. As the hearing was taking place, the White House distanced itself from any possible conclusions.

‘I think we need to see how the process works out over the next several days,’ White House Press Secretary Sarah Huckabee Sanders said. ‘And some of those questions are things you’re going to have to ask Facebook. It’s not something the federal government can weigh in at this point until the finding of that investigation, those hearings are completed.’

Some lawmakers have already introduced legislation that would require these social media giants to disclose the source of their paid advertising, just like broadcasters or publishers do.

Facebook says it’s linked about $100,000 worth of advertising to the Russian Internet Research Agency. The firms have already volunteered to disclose such information, but some lawmakers say it’s not enough and they can’t be trusted to self-regulate. The hearings will continue on Wednesday.