The social network released the information as politicians and commentators called for more to be done to police live-streaming.
Prime Minster Jacinda Ardern said Monday that the tech companies have "a lot of work" to do to curb the proliferation of content that incites hate and violence.
"So I think there are some very real discussions that have to be had about how these facilities and capabilities as they exist on social media, can continue to be offered".
Mia Garlick, director of policy for Facebook New Zealand, issued a statement saying that Facebook removed 1.5 million videos of the shooting, including 1.2 million that were blocked at upload, in the first 24 hours after the attack.
While Facebook has hired about 20,000 moderators, several media reports have highlighted the stress it puts on people to watch violent content, and problems dealing with live videos.
Ardern said New Zealand authorities and businesses did as much as they could to seek to have removed some of the footage, but ultimately it was up to those platforms to facilitate and support the removal.
On Friday, Twitter, Facebook, Instagram, YouTube and Google all said they were taking steps to remove the disturbing footage.
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A 17-minute Facebook live video was the result.
Police in New Zealand said the video was now classified as an "objectionable publication", making it an offence to distribute or possess the material. Facebook says it does not want to act as a censor, as videos of violence, such as those documenting police brutality or the horrors of war, can serve an important objective.
"Please know we are working vigilantly to remove any violent footage".
But that's just a drop in the bucket of what is needed to police the social media platform, said Siva Vaidhyanathan, author of "Antisocial Media: How Facebook Disconnects Us and Undermines Democracy". Another, a man in his late 20s, has since been charged with murder.
"These platforms are now racing to stamp out the sharing of media content for which they bear at least some responsibility", Burgess said.
Jacqueline Helfgott, a professor of criminal justice at Seattle University, said that for some, social media can be a motivator when it comes to committing a crime.
In addition to the 50 people killed, 50 others were injured and 12 remain in critical condition, officials said Sunday.
"The government has been clear that all companies need to act more quickly to remove terrorist content". The challenge here of intercepting something being live-streamed is extremely hard, where it is a terrorist attack, or other incidents we have seen such as suicides'.