The chairman of the US Senate's commerce committee is seeking answers from Facebook CEO Mark Zuckerberg over claims the social network suppressed conservative issues in its trending topics feature.
Sen. John Thune (R-S.D.) sent a letter to Zuckerberg on Tuesday, a day after a Gizmodo report cited anonymous sources who said the social network "routinely suppressed news stories of interest to conservative readers."
"Facebook must answer these serious allegations and hold those responsible to account if there has been political bias in the dissemination of trending news," Thune said in a statement. "Any attempt by a neutral and inclusive social media platform to censor or manipulate political discussion is an abuse of trust and inconsistent with the values of an open Internet."
Facebook denied the allegations Monday.
"We have in place strict guidelines for our trending topic reviewers as they audit topics surfaced algorithmically: reviewers are required to accept topics that reflect real world events, and are instructed to disregard junk or duplicate topics, hoaxes or subjects with insufficient sources," Tom Stocky, vice president of search, said in a Facebook post Monday.
The company said in a statement Tuesday that its guidelines for trending topics "require the review team members to allow all points of view."
"We have seen allegations that people did not honor the intent of those guidelines," a Facebook spokesperson said. "Although the allegations are anonymous, we take them seriously. We are continuing to investigate whether any violations took place."
The company also said it will continue to review its trending topics practices. "If we find they are inadequate, we will take immediate steps to fix them," the spokesperson said.
The senator is asking for a response no later than May 24. You can read Thune's letter in full here. Facebook said it looks forward to addressing his questions.
Update, 2:35 p.m. PT: Added comments from a Facebook representative.