Facebook founder and CEO Mark Zuckerberg addressed the criticisms that his company has been promoting fake news in a lengthy post on the site.

Since Facebook fired the editors who used to curate its “trending” topics, Facebook has received criticisms that its algorithm proliferates misinformation throughout the site and is unable to distinguish facts from fiction.

These criticisms came into focus during the 2016 presidential campaigns. Fake news about both candidates was rampant, and some have accused Facebook of helping Donald Trump win the election by failing to address the “fake news” problem. In fact, reports showed that fake viral news got more likes and shares near the end of the election than did real news.

In his recent Facebook post, Zuckerberg says the company has a plan to start combating the fake news more vigorously. He points out that already the company has tools in place that let users report suspicious links.

“Anyone on Facebook can report any link as false, and we use signals from those reports along with a number of others—like people sharing links to myth-busting sites such as Snopes—to understand which stories we can confidently classify as misinformation," he said. "Similar to clickbait, spam and scams, we penalize this content in News Feed so it's much less likely to spread.

However, he said that battling fake news has proven difficult “both technically and philosophically.”

“We need to be careful not to discourage sharing of opinions or mistakenly restricting accurate content. We do not want to be arbiters of truth ourselves, but instead rely on our community and trusted third parties.”

Despite these concerns, given the gravity of the situation, Facebook is working on projects it believes could solve the fake news problem without limiting free speech, and Zuckerberg shares specific examples in his post. They include better technical tools that can detect fake stories, working with third party fact checkers, easier avenues for readers to report fake stories, as well as labels on stories that have been flagged as scams.

Another ambitious project of Facebook’s is “disrupting fake news economics,” says Zuckerberg. “A lot of misinformation is driven by financially motivated spam. We're looking into disrupting the economics with ads policies like the one we announced earlier this week, and better ad farm detection.”

In a recent interview with the Washington Post, one fake news writer said he makes $10,000 a month from AdSense and uses Facebook to help boost his site traffic. The average journalist makes less than $50,000 annually.

Zuckerberg says he isn’t confident that all these projects will help solve the fake news crisis on Facebook, “But I want you to know that we have always taken this seriously, we understand how important the issue is for our community and we are committed to getting this right.”

You can read his Facebook post in full here.