Facebook’s efforts to limit the spread of coronavirus misinformation are running into a problem: groups.

Dozens of public and private Facebook groups totaling hundreds of thousands of members have become a haven for conspiracy theories, medical equipment promotion and unproven cures related to the new coronavirus, according to an analysis by NBC News.

In one popular group, members suggested the coronavirus was a Democratic plot. In another, it was said to be orchestrated by the “deep state.” In one, it was a bioweapon made by the Chinese government. In another, it was deemed an insidious plan by vaccine researchers in the United States to make money. Across dozens of other groups, members offered links to their own websites, where people can buy elderberry, or Vitamin C, or masks, to protect you from the coronavirus.

This despite the fact that there is currently no scientifically validated treatment for the coronavirus.

The groups present a difficult challenge for Facebook as it has moved to crack down on misinformation, scam artists and other bad actors while also promoting its groups feature, which the social network has emphasized in recent years.

In recent weeks, Facebook has made sweeping moves on its platform to curtail misinformation around the coronavirus and promote reliable information on its spread. On Tuesday, CEO Mark Zuckerberg posted an update on Facebook’s response to the coronavirus, which has included popups that direct users searching for information about the disease to sites belonging to trusted websites like those for the World Health Organization. The company has also provided the WHO with “as many free ads as they need,” and continues to ban ads designed to promote fake coronavirus cures, he wrote.

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But Zuckerberg drew a familiar line against policing what he has long seen as free speech.

“It's important that everyone has a place to share their experiences and talk about the outbreak, but as our community standards make clear, it's not okay to share something that puts people in danger,” he wrote.

Coronavirus misinformation highlights a recurring issue with misinformation on Facebook groups. Facing criticism, Facebook ramped up enforcement of its community standards last year for the tens of millions of active groups on its platform. The company announced a concentrated push on its Groups feature in 2017. More than 400 million users are now in “meaningful groups,” and the feature has been at the center of new advertisements from New York City subways to Super Bowl ads.

Joan Donovan, the director of Harvard University’s Technology and Social Change Research Project, said Facebook’s announcement to remove misleading content on the coronavirus was “hopeful and ambitious” but added that the company still had work to do.

“Manipulators will continue to use keyword squatting in private groups to seed health misinformation and scams,” Donovan said. “The platform is too big for proper moderation, especially when most people posting about coronavirus are seeking information and asking about potential cures.”

WhatsApp, the popular messaging app owned by Facebook, has also proven to be a difficult place for the company to manage coronavirus misinformation and blatantly racist material in the form of memes and jokes. Misinformation related to the virus has spread in Africa, India and many other parts of the world, aided in large part due to WhatsApp forwarded messages.

A Facebook spokesperson said in an email that the company was “focused on connecting people with accurate information and removing harmful misinformation related to COVID-19, including in Groups.” COVID-19 is the name given to the disease caused by the new coronavirus.

“We already reduce the distribution of any groups that repeatedly share false news, and in the coming days we’ll begin removing coronavirus related groups and pages from the recommendations we show people,” the spokesperson said.

None of the most popular Facebook coronavirus groups appear to be run by medical professionals or health experts.

The administrator for ”CoronaVirus,” a group with more than 66,000 members, works for an information technology company in Istanbul, according to his Facebook profile. Its rapid growth and thousands of posts a day led one moderator to post, “The group has grown quite a lot in numbers, and with such, we are no longer able to manually confirm news.”

Coronavirus misinformation and fake cures have also found life in existing groups meant to spread conspiracies.

In recent weeks, the coronavirus has dominated conversation in Stop Mandatory Vaccination, Facecbook’s most popular anti-vaccination group, with 180,000 members. Among thousands of posts, members suggest without evidence that the coronavirus can be cured with homeopathic remedies or vitamins, and that the outbreak was orchestrated as part of a nefarious plot by the government and “Big Pharma.”

The owner of Stop Mandatory Vaccination, supplement advocate Larry Cook, uses his group to spread a conspiracy that the coronavirus is a government plan “to force-vaccinate every man, woman, and child on the planet.” And although Facebook has banned ads promoting unproven cures, Cook utilizes features like Facebook Live to promote products and share links to his website where he sells vitamins and books that he claims will protect against the coronavirus.

Cook did not respond to a request for comment.