The scandalous tale about Facebook's news "curators" and allegations that the Trending Topics section took on some anti-conservative bias at the hands of those curators has blown up Tuesday with CEO Mark Zuckerberg receiving a letter from the US Senate Commerce Committee asking a series of questions it wants answered by Facebook staff. Among them: If Facebook has "rigorous guidelines in place for the review team" on Trending Topics as a rep from the team says in a statement, what are they and how long have they been in place?

Trending Topics team lead Tom Stocky issued the statement late Monday after Gizmodo released the second part of their story, which drew on quotes from former Facebook contract employees. Those anonymous employees say they were hired for their journalism backgrounds to help manage the Trending feed, and allege that trending news from conservative news sources was routinely blacklisted based on the biases of whoever was on duty at the time.

Says Stocky:

We take these reports extremely seriously, and have found no evidence that the anonymous allegations are true.

Facebook is a platform for people and perspectives from across the political spectrum. There are rigorous guidelines in place for the review team to ensure consistency and neutrality. These guidelines do not permit the suppression of political perspectives. Nor do they permit the prioritization of one viewpoint over another or one news outlet over another. These guidelines do not prohibit any news outlet from appearing in Trending Topics.
We are proud that, in 2015, the US election was the most talked-about subject on Facebook, and we want to encourage that robust political discussion from all sides. 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. Facebook does not allow or advise our reviewers to systematically discriminate against sources of any ideological origin and we've designed our tools to make that technically not feasible. At the same time, our reviewers' actions are logged and reviewed, and violating our guidelines is a fireable offense.

The GOP led Commerce Committee, however, didn't blink an eye before starting this inquiry, given just how influential they know Facebook could be as a news source in this year's election. Any hint that Republicans may suffer any further from the suppression of good news about them, for obvious reasons, has them foaming. And they want to take this discussion back to January 2014, in fact.

Per their tersely worded letter, which you can read in full on Gizmodo:

1) Please describe Facebook’s organization structure for the Trending Topics feature, and the steps for determining included topics. Who is ultimately responsible for approving its content?

2) Have 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?

3) What steps is Facebook taking to investigate claims of politically motivated manipulation of news stories in the Trending Topics section? If such claims are substantiated, what steps will Facebook take to hold the responsible individuals accountable?

4) In a statement responding to the allegations, Facebook has claimed to have “rigorous guidelines in place for the review team” to prevent “the suppression of political perspectives” or the “prioritization of one viewpoint ver another or one news outlet over another.”

a. When did Facebook first introduce these guidelines?

b. Please provide a copy of these guidelines, as well as any changes or amendments since January 2014.

c. Does Facebook provide training for its employees related to these guidelines? If so, describe what the training consists of, as well as its frequency.

d. How does Facebook determine compliance with these guidelines? Does it conduct audits? If so, how often? What steps are taken when a violation occurs?

5) Does Facebook maintain a record of curators decisions to inject a story into the Trending Topics section or target a story for removal? If such a record is not maintained, can such decisions be reconstructed or determined based on an analysis of the Trending Topics product?

a. If so, how many stories have curators excluded that represented conservative viewpoints or topics of interest to conservatives? How many stories did curators inject that were not, in fact, trending?

b. Please provide a list of all news stories removed from or injected into the Trending Topics section since January 2014.

The letter asks for the company to "arrange for your staff including employees responsible for trending topics to brief committee staff on this issue." It's unclear how or when that briefing may occur.

On Monday, after the allegations of anti-conservative bias arose, Facebook told SF Gate that they would be investigating these, and the post by Stocky which went up just before midnight appears to suggest the conclusion of that investigation. Says Stocky, "We take these reports extremely seriously, and have found no evidence that the anonymous allegations are true." But, he also concludes, "Our review guidelines for Trending Topics are under constant review, and we will continue to look for improvements."

Zuckerberg has previously made some grand statements about how he hopes that Facebook will ultimately be the "primary news experience people have."

Stay tuned to see if Zuck will actually wear a hoodie to a Senate committee hearing.

Previously: Facebook's 'News Curators' Choose Trending Topics, Suppress Conservative News, Say Former Employees