By Melony Roy

By Melony Roy

PHILADELPHIA (CBS) — Facebook has been under fire this week over claims that some of its news curators prevented conservative outlets from showing up in its “Trending Topics” section.

The social network’s founder is speaking out.

Facebook CEO Mark Zuckerberg say his company is investigating a report accusing it of a liberal news bias, but has so far found “no evidence” that it’s true.

The social network has released a 28-page internal document detailing how computer algorithms and news editors determine what news stories are the most popular and outlining editorial guidelines for the team of editors who oversee the “Trending Topics” feature.

In a Facebook post Thursday night, Zuckerberg says that being open to all viewpoints is at the “core of everything Facebook is and everything I want it to be” and “every tool they build is designed to give more people a voice and bring our global community together.”

Zuckerberg’s comments come after the network was accused of suppressing conservative news sites and injecting a liberal bias into its “Trending Topics” section, according to anonymous sources in a Gizmodo report earlier this week.

Zuckerberg says he plans to invite leading conservatives and people from across the political spectrum to discuss their points of view in the coming weeks.