The House select committee formed to investigate the Jan. 6 riot at the U.S. Capitol issued subpoenas to four major social media companies on Thursday as it questions the role of “misinformation” in proving the violence and what the companies knew about the riot or the “spread of extremism that enabled the attack.”

Alphabet, Meta, Reddit, and Twitter received subpoenas. The committee in August 2021 requested the companies voluntarily turn over information, but letters to the companies sent alongside subpoenas Thursday alleged they failed to produce documents to the committee in a timely manner or, in Reddit’s case, refused altogether.