Facebook CEO Mark Zuckerberg. Win McNamee/Getty Images US senators have asked Facebook for more information in the wake of a report alleging that the social network has been suppressing conservative news and media outlets.

Gizmodo published a bombshell report earlier this week alleging that curators who control the "Trending" news bar on the side of the social network routinely choose not to feature conservative topics and news outlets, while favouring others like activist movement Black Lives Matter.

In a Facebook post published early Tuesday morning, the social network's VP of search Dan Stocky finally denied the reports, writing that "we take these reports extremely seriously, and have found no evidence that the anonymous allegations are true."

But the debate is rumbling on, and raises broader questions about whether Facebook's reportedly largely young and liberal news curators have implicit biases affecting what the Trending bar features, as well as Facebook's responsibilities as a dominant media platform.

The latest development: The US Senate Committee on Commerce, Science, and Transportation sent a letter to Mark Zuckerberg with a list of five questions about the feature and the allegations, reports Gizmodo.

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?" One question asks.

Another asks for a copy of the "guidelines" that Facebook has to prevent "the suppression of political perspectives."

A third requests "a list of all news stories removed from or injected into the Trending Topics section since January 2014."

The letter asks for the information "as soon as possible, but no later than May 24, 2016. In addition, please arrange for your staff, including employees responsible for Trending Topics, to brief Committee staff on this issue," it says.

Facebook said it's "continuing to investigate whether any violations took place," and looks forward to address Sen. Thun's questions.

Here's Facebook's full statement:

Facebook is deeply committed to being a platform for people and perspectives of all viewpoints. Trending Topics is designed to surface popular conversations — no matter where they fall on the political spectrum — and our guidelines 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. 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. We have received Sen. Thune's request for more information about how Trending Topics works, and look forward to addressing his questions.

Here's the full letter:

Gizmodo

Gizmodo