Senate Intelligence Committee Vice Chairman Mark Warner asks questions during a committee hearing on Capitol Hill on June 13, 2017. The committee has invited tech company executives to an an open hearing. (Jacquelyn Martin/AP)

The Senate Intelligence Committee has invited tech giants Facebook, Twitter and Google to testify in an open hearing as part of the panel's probe of Russian interference in the 2016 presidential election, according to a senate aide.

The hearing, which is set to take place on Nov. 1, is expected to be the second time the tech companies' executives will speak with the committee. Committee investigators have already conducted a closed-door interview with Facebook and are planning another with Twitter executives on Thursday; the committee is planning to speak with representatives of Google before the open hearing as well.

Leaders of the House Intelligence Committee announced on Wednesday that they too plan to hold an open hearing with tech company executives in October. Rep. Adam B. Schiff (Calif.), the ranking Democrat on the committee, said in an interview that while invitations have not been sent out yet, the committee is hoping to include Facebook, Google and Twitter, as well as a number of industry experts. House Intelligence Committee investigators are also planning to speak behind closed doors with Twitter representatives on Thursday, he added.

The three tech giants seized the interest of committee investigators after it came to light that Russia had paid Facebook to place thousands of targeted ads, exploiting racial and religious tensions in the United States. Facebook has said that about $100,000 worth of Facebook ads had been purchased through 470 fake accounts.

Facebook is in the process of turning over 3,000 Russian-bought ads to the House and Senate Intelligence Committees so that they can review them. Schiff said Wednesday that "it's my belief that we're going to get more than just the advertisements."

"We're certainly going to need more than just the advertisements," he said.

One key question for both House and Senate investigators is whether the Russians alleged to be behind these Facebook ad campaigns and Twitter bots promoting divisive literature acted alone, or whether they relied on a more knowledgeable source to target likely Trump voters — potentially even the Trump campaign itself.

Schiff said that lawmakers are seeking data and analytics information not only from the tech companies, but from the Trump campaign as well, to make comparisons and shed light on whether there could have been any coordination.

Schiff is eager to make much of the information about the advertisements public, to give people a sense of which ads may have been purchased to wield influence during the election season. He noted, however, that certain ads might first have to be scrubbed before they could be made public, because many use expropriated images or other personally identifiable information of individuals who may have no idea they had been made part of a Russian advertising operation.