Executives from Facebook, Alphabet Inc’s Google and Twitter have been asked to testify to the U.S. Congress in coming weeks as lawmakers probe Russia’s alleged interference in the 2016 U.S. election, committee sources said on Wednesday.

A Senate aide said executives from the three firms had been asked by the Senate Intelligence Committee to appear at a public hearing on Nov. 1.

The leaders of the House of Representatives Intelligence Committee said the panel would hold an open hearing next month with representatives from unnamed technology companies in an effort to “better understand how Russia used online tools and platforms to sow discord in and influence our election.”

Representatives for Facebook and Google confirmed they had received invitations from the Senate committee but did not say whether the companies would attend. Twitter did not immediately respond to requests for comment.