A top Republican senator on Tuesday demanded answers from Facebook CEO Mark Zuckerberg over allegations that the social media giant’s trending news feature omits topics popular with conservatives.

“Facebook must answer these serious allegations and hold those responsible to account if there has been political bias in the dissemination of trending news,” said Senate Commerce Committee Chairman John Thune John Randolph ThuneWhat Senate Republicans have said about election-year Supreme Court vacancies The Hill's 12:30 Report - Presented by Facebook - Don't expect a government check anytime soon The Hill's Morning Report - Sponsored by The Air Line Pilots Association - Trump contradicts CDC director on vaccine, masks MORE (R-S.D.) 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.”

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Thune sent a letter to Zuckerberg after Gizmodo reported allegations that the human curators behind the company's "Trending" feature omitted topics popular with conservatives and didn't include stories from conservative news outlets.

Thune's letter to Zuckerberg asks a number of questions, including whether "Facebook news curators in fact manipulated the content of the Trending Topics section, either by targeting news stories related to conservative views for exclusion or by injecting non-trending content."

A Facebook executive said Tuesday that an initial review found "no evidence" to support the bias charges.

The South Dakota Republican also asked for more details on the guidelines Facebook has said stop the curators of the trending section from suppressing conservative news outlets.

"If Facebook presents its Trending Topics section as the result of a neutral, objective algorithm, but it is in fact subjective and filtered to support or suppress particular political viewpoints, Facebook’s assertion that it maintains a ‘platform for people and perspectives from across the political spectrum’ misleads the public,” Thune wrote to Zuckerberg.

Facebook confirmed that they have received and are reviewing the letter.

In a statement, a Facebook spokesperson reiterated that the curators were subject to guidelines meant to guard against political bias.

"We have seen allegations that people did not honor the intent of those guidelines," the spokesperson said. "Although the allegations are anonymous, we take them seriously. We are continuing to investigate whether any violations took place."

"As we investigate, we will also keep reviewing our operational practices around Trending Topics — and if we find they are inadequate, we will take immediate steps to fix them," the spokesperson continued. "We have received Sen. Thune's request for more information about how Trending Topics works, and look forward to addressing his questions."

One of Thune’s Democratic colleagues quickly jumped on his letter as evidence that Republicans had the wrong priorities.

“The Republican Senate refuses to hold hearings on Judge Garland, refuses to fund the President’s request for Zika aid and takes the most days off of any Senate since 1956, but thinks Facebook hearings are a matter of urgent national interest,” said Adam Jentleson, a spokesman for Senate Minority Leader Harry Reid Harry Mason ReidSenate Republicans signal openness to working with Biden Mellman: The likely voter sham Bottom line MORE (D-Nev.).

— Last updated at 3:58 p.m.