(CNN) Sen. Mark Warner says the "million-dollar question" still unanswered about the Facebook election ads sold to Russian-linked accounts was how the Russians knew whom to target on Facebook.
Warner, the top Democrat on the Senate intelligence panel, told CNN the committee expects this week to begin viewing the 3,000 Russian-linked Facebook ads, which Facebook earlier this month disclosed were connected to more than 450 inauthentic accounts. Facebook agreed last week to turn the ads over to the House and Senate intelligence committees.
Warner's burning question involves not just the content of the ads but how they were deployed.
"Did they know this just by following political news in America? Did they geo-target both geography and by demographics in ways that at least at first blush appear pretty sophisticated? These are the kind of questions that we need to get answered and that's why we need them in a public hearing," Warner said.
The Virginia Democrat said it was "too early to tell" whether any Trump campaign officials were associated with the ads.
"I raised this issue back last winter at that point Facebook was dismissive that there was anything there. We've now seen that there was a lot there in terms of paid advertising, fake accounts, pushing people towards rallies, trying to sow division and chaos," Warner said. "And that's why I'm anxious to review the materials they are sending in to the committee."
But Sen. Richard Burr, the chairman of the committee, said there's "no evidence yet" that Russians and Trump officials colluded on the Facebook ads, though he said it's an area the committee continues to investigate. Burr said the effort appeared to be more about sowing chaos on both sides of the political spectrum.
"The social media platforms look to be a tool that were utilized by a foreign power to impact the 2016 elections," Burr said. "Is there collusion? None that anybody can see."
The Senate intelligence panel has met with Facebook officials in a closed session, and Twitter officials are coming to talk to the intelligence panel on Thursday in a closed session.
"A lot of the same claims that have been made about Facebook, have also been made about Twitter," Warner said, adding that it was "too early" to tell if they would be cooperative with congressional efforts to determine the scope of Russian attempts to use social media in the 2016 election.
Burr says he wants to have a public hearing with Facebook and other social media companies as early as next month. But the North Carolina Republican does not think it's the committee's job to make the ads public when they are given to the committee.
"We don't routinely release any information that's shared with the committee and I'd like to keep the committee in that mode," he said.
This story has been updated.