WASHINGTON - The U.S. House committee investigating the January 6 attack on the Capitol subpoenaed Meta, Alphabet, Twitter and Reddit on Thursday, seeking information about how their social media platforms were used to help fuel misinformation in a failed bid to overturn the 2020 presidential election.

'Two key questions for the Select Committee are how the spread of misinformation and violent extremism contributed to the violent attack on our democracy, and what steps - if any - social media companies took to prevent their platforms from being breeding grounds for radicalizing people to violence,' the House Select Committee's chairman, Representative Bennie Thompson, said in a statement.

'It's disappointing that after months of engagement, we still do not have the documents and information necessary to answer those basic questions.'

The subpoenas are the latest development in the panel's investigation into the causes of the attack on the Capitol by then-President Donald Trump's supporters, and the role played by Trump, who has pushed false claims that he lost a rigged election to Joe Biden.

The committee has issued more than 50 subpoenas and heard from more than 300 witnesses. It is expected to release an interim report in the summer and a final report in the fall.

Spokespeople for the four social media companies did not immediately respond to requests for comment.

Social media platforms were widely blamed for amplifying calls to violence and spreading misinformation that contributed to the January 6 attempt to violently overturn the election results.

Meta Chief Executive Mark Zuckerberg, Alphabet, and Google CEO Sundar Pichai, and former Twitter CEO Jack Dorsey were grilled by lawmakers last March in a hearing on misinformation about the role of their companies in the Capitol riot.

In a letter sent this week to Zuckerberg, Representative Thompson said that 'despite repeated and specific requests for documents' related to Facebook's practices on election misinformation and violent content, the committee had still not received these materials. Letters to the other three CEOs contained similar criticisms.