In early May, Facebook said it was hiring an additional 3,000 people to identify and remove violent and hateful content.
The announcement came after several people posted videos of murders and suicides that stayed on Facebook for hours.
In a Facebook post, CEO and co-founder Mark Zuckerberg called the videos "heartbreaking." He said the new employees will work with about 4,500 existing ones to find and remove such content as quickly as possible.
Facebook receives millions of reports about content each week, said Zuckerberg.
In addition to humans, the company uses technical tools to identify questionable material. But with Facebook's nearly 2 billion monthly active users, identifying and blocking banned content is difficult.
Britain's Guardian newspaper recently reported on Facebook's policies for the removal of certain kinds of content. The newspaper said it gained possession of private training documents and other materials used as guidelines for Facebook employees.
The documents have not been released publicly and Facebook did not comment on the Guardian report.
The Guardian report says Facebook policy permits some posts containing violent language, and not others. This reportedly can depend on whether the content relates to what Facebook considers protected or non-protected people or groups.
The guidelines also reportedly permit photos of animal abuse to be posted, if the most extreme images are marked as "disturbing."
Monica Bickert is Facebook's head of global policy management. She says the company's goal is to keep users safe, while also permitting individual free speech.
"This requires a lot of thought into detailed and often difficult questions, and getting it right is something we take very seriously," she said.
Emma Llanso is director of the Free Expression Project at the not-for-profit Center for Democracy & Technology. She says the Facebook documents show how difficult it can be for social media companies to balance free expression with content controls.
"I think it can help more people understand what a challenging task we all face in figuring out what are the sorts of speech and the kinds of content that we all find acceptable on our social media services..."
She said one way for social media companies to balance these issues is to provide better filtering tools for users to block content themselves.
"You have got to look more to the ability for people to create their own filters or blacklists, or categories of things that they just don't want to see. That's the sort of response that really puts the power in the hand of the individual user..."
Facebook and other social media services – including Twitter, WhatsApp and Telegram - have been criticized for not doing enough to block content linked to terrorist groups.
The recent suicide bombing in Manchester, England led some officials to repeat calls for social media companies to do more to stop terrorist activity.
The British government has proposed legislation requiring social media companies to permit them access to encrypted messages sent through social media services.
Thomas Zeitzoff is a professor at American University in Washington, D.C. He studies the effects of social media on conflicts. He says one problem with trying to limit terrorist activities on Facebook and Twitter is that groups usually find ways around the restrictions.
"What you've seen the groups do is they've migrated to Telegram, WhatsApp and other kinds of encrypted social media applications that make it much harder for governments to track."
Even as some governments call for stricter limits on social media, they also use the services themselves to gather information on terror groups and to help with investigations.
Zeitzoff says social media also publicizes attacks globally and can give terrorists a way to get their message out to the whole world.
"There can be this concern that it broadens and amplifies the message and terrorizes people more. But too, it also can inspire people, because some people want to be famous or they see some kind of identification with the attacker that carried it out."
I'm Bryan Lynn.