“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 the committee’s chairman,

Rep. Bennie Thompson

(D., Miss.). “It’s disappointing that after months of engagement, we still do not have the documents and information necessary to answer those basic questions.”

The committee said it has been investigating the role of social-media platforms in efforts to overturn the 2020 election results and what the companies might have known about the spread of extremism in the lead-up to Jan. 6, 2021.

Mr. Thompson said in a letter to Alphabet that its YouTube was used for communications related to the Jan. 6 attack and to spread misinformation about the election. In a letter to Meta, Mr. Thompson cited public reports that the company’s platforms, which include Facebook, were used to spread messages of violence and for efforts to mobilize people to challenge the election results.

“We’ve been actively cooperating with the Select Committee since they started their investigation, responding substantively to their requests for documents, and are committed to working with Congress through this process,” Alphabet said in a statement.

Meta spokesman Andy Stone said that “Meta has produced documents to the committee on a schedule committee staff requested—and we will continue to do so.”

A Reddit spokesperson said the company had received the subpoena and will continue to work with the committee on its requests.

Twitter declined to comment.

The committee’s latest round of subpoenas comes a day after it asked House Republican leader

Kevin McCarthy

of California to voluntarily provide information about his conversations with then-President

Donald Trump

before, during and after the riot. Mr. McCarthy rejected the request, saying it was politically motivated.

The panel is led by Mr. Thompson and Vice Chairwoman

Liz Cheney

(R., Wyo.). The investigation is looking into the causes and security failures of the Jan. 6 attack on the Capitol, when supporters of Mr. Trump stormed the building and temporarily disrupted the certification of Democrat

Joe Biden’s

presidential election win.

The panel has demanded records from a number of social-media companies over the past several months. The committee also has contacted former Trump administration officials and allies for testimony or documents.

The panel also asked to meet with Reps.

Scott Perry

(R., Pa.) and

Jim Jordan

(R., Ohio). Both rejected the committee’s request, saying the panel is illegitimate.

—Salvador Rodriguez contributed to this article.

Write to Alexa Corse at alexa.corse@wsj.com