The taking down of a viral video by social media companies has reignited a highly-charged controversy in the US over the use of the anti-malaria drug, hydroxychloroquine.
In the video, members of the group America's Frontline Doctors promote it both as a preventative measure and as a cure for Covid-19.
The World Health Organization (WHO) say "there is currently no proof" that hydroxychloroquine is effective as a treatment or prevents coronavirus.
The video was broadcast online by right-wing online platform Breitbart, viewed over 17 million times on Facebook. It was also shared on Twitter by Donald Trump and many of his supporters.
The president's son, Donald Jnr, was suspended from tweeting for 12 hours by Twitter after he posted it on his account.
What does the video claim?
The video, a 45-minute livestream of the first day of a "White Coat" summit by the group, was posted to Facebook, Twitter and YouTube by Breitbart and quickly went viral.
"The virus has a cure, it's called hydroxychloroquine, zinc, and Zithromax," says one of the doctors in the video.
"You don't need masks. There is a cure. I know they don't want to open schools. No, you don't need people to be locked down. There is prevention and there is a cure."
The Facebook video, as well as racking up millions of views, was shared nearly 600,000 times before it was taken down.
The hashtag #hydroxychloroquine was tweeted more than 153,000 times, becoming one of Twitter's top trends in the US overnight.
Multiple versions of the video continue to be widely shared on social media.
According to data from the Facebook-owned social media analytics tool CrowdTangle, public posts in the last 24 hours containing the word hydroxychloroquine have had 6.6 million engagements (likes, shares, views, comments and reactions) on Facebook and Instagram despite the removal of several versions of the video.
In a statement to BBC News, Twitter said: "Tweets with the video are in violation of our Covid-19 misinformation policy. We are taking action in line with our policy here."
"We've removed this video for sharing false information about cures and treatments for Covid-19," Facebook told the BBC, confirming it was also removing other versions of the video.
YouTube told the BBC: "We have removed the video for violating our Covid-19 misinformation policies."
BBC News also approached Breitbart, the White House and America's Frontline Doctors for comment.
What is the evidence for hydroxychloroquine?
The drug is a well-known treatment for malaria and was first touted by President Trump in March in connection with Covid-19.
The WHO says: "While several drug trials are ongoing, there is currently no proof that hydroxychloroquine or any other drug can cure or prevent COVID-19."
"The misuse of hydroxychloroquine can cause serious side effects and illness and even lead to death," it adds.
A study conducted by Oxford University found the drug was not effective against Covid-19 in hospitalised patients.
Its effectiveness when used early on during treatment is still being studied, as is its use as a preventative measure.
Medical trials have so far been inconclusive and the results of larger-scale randomised studies will be needed to know if it's effective or not.
In July, the US Food and Drug Administration warned against the use of the drug outside a hospital setting because of possible risks to the heart from taking it.
Who are the doctors?
America's Frontline Doctors is a collection of physicians critical of the scientific consensus around the pandemic. Their event was backed by the Tea Party Patriots, a conservative organisation seeking to re-elect President Trump.
Its founder, Simone Gold, organised a letter to Mr Trump calling for an end to lockdown measures in May.
Participants were encouraged to seek out interviews with social media influencers as the best way to connect with Americans.
There has been intense debate on social media in recent months about hydroxychloroquine, and influential Fox News anchors have also run segments favouring the drug.
Ralph Norman, a Republican member of the House of Representatives, was standing alongside the doctors when they delivered their news conference.
The debate has been increasingly dividing Americans along political lines, with proponents of hydroxychloroquine pointing to President Trump's support of it while accusing critics of covering up its potential effectiveness.