Following claim Facebook suppresses conservative views in trending news, top Republican senator John Thune sent a terse letter to Mark Zuckerberg

A top US Senate Republican demanded on Tuesday that Facebook explain allegations that it suppressed conservative articles on users homepages as part of a political agenda.

Senator John Thune, a party leader and chairman of the Senate commerce committee, which has jurisdiction over technology firms, sent a terse letter to Facebooks CEO, Mark Zuckerberg, asking him to explain accusations that he misleads the public.

The social media juggernaut faces tough questions this week from conservatives following a series of stories in Gizmodo that its news curators injected stories into the trending articles section in the top-right corner of its home page. Many users, apparently including Thune, assumed the articles in that space were the ones users shared the most on the service.

Citing one former anonymous curator, Gizmodo reported that Facebook news contractors were told to suppress content of interest to conservative readers. Facebook has denied that allegation and said it has guidelines to ensure consistency and neutrality in the topics it promotes.

Late Monday, Tom Stocky, Facebooks vice-president of search, wrote in a Facebook post: We take these reports extremely seriously, and have found no evidence that the anonymous allegations are true. He added that the accused censorship was technically not feasible with their tools.

Regardless of this specific incident, the allegations reflect broader unease about how Facebook wields its influence in what media its users read. By traditional measures, Facebooks trending section could be considered the most popular front page on the internet.

The mainstream media is accused of bias regularly, and deciding which stories get the best placement is an inherently subjective process. But rightly or wrongly, many users expect that Silicon Valley somehow has found a way to neutralize the news business.

Given American free-speech law, its also unclear if the US Senate has any jurisdiction over how Facebook or any other company promotes certain articles.

For instance, Thune asks Facebook to quantify, all news stories removed from or injected into the Trending Topics section since January 2014. Its unclear how Facebook would create such a list that covers more than two years of digital news.

In a written statement, a Facebook representative said the company was continuing to investigate whether any violations took place.

As for the letter from Congress, Facebook said, We have received Sen Thunes request for more information about how Trending Topics works, and look forward to addressing his questions.

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