The House Select Committee investigating the Capitol riot has issued subpoenas to four of the internet's biggest social media firms — Twitter, Reddit, Facebook's parent company Meta, and Google's parent company Alphabet — for records related to the spread of misinformation around the 2020 election.

The panel initially asked for such records in August but is now demanding the information again after finding that they gave "inadequate responses," the committee wrote in a statement Thursday.

"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," said Democratic Rep. Bennie Thompson of Mississippi, chairman of the committee.

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

The statement said YouTube, which Alphabet owns, served as a "significant communications" platform for people who planned and executed the Capitol attack on January 6, 2021. The committee noted that there were several live streams on YouTube of the siege as it was taking place.

And the panel pointed to the subreddit "r/The_Donald" as a community that eventually moved off Reddit but later created a website that "hosted significant discussion and planning" related to the attack.

Meta's platforms were used to spread misinformation, hatred, and election conspiracy theories, and alongside Twitter, were also used to coordinate the assault, the committee also said.

The Select Committee addressed each company's CEO with an individual letter from Thompson.

Alphabet, Thompson wrote, failed to disclose information that's "critical" to the committee's investigation. For example, it didn't explain how it moderates content and whether or why it didn't take action against former President Donald Trump's YouTube account. After the Capitol siege, Trump's account was suspended by Alphabet for "violating our policies for inciting violence."

Meta hasn't told the committee why it stood down its Civic Integrity team, which was used to combat election misinformation and disbanded after November 2020, despite the panel's multiple requests for that information, Thompson wrote. Nor has it delivered "critical internal and external analyses" on misinformation on its platform or its efforts to stop such false information, he added.

A Meta spokesperson told Insider in a statement that the company has "produced documents to the committee on a schedule committee staff requested — and we will continue to do so."

Reddit still hasn't "committed to a thorough review of its records" for the investigation since being asked to do so in August, and "refused to produce internal documents" to support its public statement that it had nothing to do with the Capitol attack, Thompson said.

In response to queries about the subpoena, a Reddit spokesperson told Insider: "We received the subpoena and will continue to work with the committee on their requests."

And Twitter failed to disclose documents regarding how it was warned that its platform was being used to incite violence on January 6, the congressman wrote.

Alphabet and Twitter did not immediately respond to Insider's requests for comment.