Facebook has come under fire this week after a hoax story about women being abducted in white vans went viral on its platform. The site’s algorithms are thought to have perpetuated the circulation of the story.

The story resulted in a TV appearance on Monday by Baltimore’s mayor, Jack Young, who warned citizens that the white vans are abducting women for sex trafficking and selling their body parts, even though the claims have not been substantiated. “It’s all over Facebook,” he told a local news station.

The platform says it is is now trying to stop the misinformation from spreading even further – by limiting the circulation of viral posts that are perpetuating it.

This week, the Guardian uncovered a far-right network pushing out thousands of fake news articles about the US congresswomen Ilhan Omar and Rashida Tlaib. When the Guardian notified Facebook of its investigation, the company removed several pages and accounts – but not because they were spreading misinformation. The media platform removed only content that “appeared to be financially motivated”.

Here are some other unsubstantiated stories that remain on the platform.

1 Trump’s grandfather, the pimp, and his father, the KKK member

Frederick Trump. Photograph: Wikipedia

A story from the American Herald Tribune claiming that Donald Trump’s grandfather was a pimp and a tax evader continues to circulate on Facebook. It also claims that the president’s father, Fred Trump, was a KKK member.

The article was thought to be shared almost 30m times, despite having no substantial evidence to support its claims. Fred Trump was detained during a KKK protest in Queens, New York, in 1927, but he was released without charges.

Trump’s grandfather, Frederick Trump, owned hotels and restaurants in Seattle. The Trump family biographer Gwenda Blair said that one such restaurant in the middle of Seattle’s red-light district, the Dairy, advertised “rooms for ladies” – commonly thought to be a euphemism for prostitution. However, there is no evidence that he was a pimp – something Blair herself stated.

2 Ilhan Omar attended an al-Qaida training camp

A Somali army female recruit checks her automatic weapon at a military training camp in Mogadishu. The picture was taken in 1978, before Ilhan Omar was born. Photograph: Tomkins/AP

Another false story that had an estimated 77,000 views claims that Omar attended an al-Qaida training camp. It comes from a photo taken at a Mogadishu training camp by the Associated Press in 1978, three years before Omar was born.

Facebook flagged the post as fake as part of its goal of reducing fake news on the site, but it continues to circulate elsewhere online. In October, the North Dakota state senator Oley Larsen shared the debunked post on Facebook.

3 Alexandria Ocasio-Cortez wants to ban motorcycles

Alexandria Ocasio-Cortez in Washington DC on 14 November. Photograph: Erin Scott/Reuters

A story claiming that the New York congresswoman Alexandria Ocasio-Cortez wants to ban motorcycles in the US was shared online more than 12m times on Facebook, and has since been debunked.

It comes from the website Taters Gonna Tate and quotes Ocasio-Cortez as saying: “Besides like, what I just said? A lot of these like, motorcycle people, OK, they’re like: ‘Ooh, look at me, I’m all old and fat and tough and I voted for Trump and smell like wet dog.’”

Although the website is clearly satirical, articles written on it have been taken seriously – including one that claims Ocasio-Cortez believes that soldiers are paid too much. A Louisiana police officer shared that article in a Facebook post in July, calling Ocasio-Cortez a vile idiot and saying she should be shot.

4 Holocaust denial content

Mark Zuckerberg in San Jose, California, on 1 May 2018. Photograph: Marcio Jose Sanchez/AP

Facebook has repeatedly made the case that it is not the job of the platform to remove Holocaust denial content. Mark Zuckerberg memorably defended the rights of Facebook users who post Holocaust denial content in 2018, saying that he didn’t “think that they’re intentionally getting it wrong”.

He later added that he found Holocaust denial “deeply offensive”, but maintained that the platform’s role is not to remove things that people get wrong.