Facebook has lifted a ban on posts claiming Covid-19 was man-made, following a resurgence of interest in the “lab leak” theory of the disease’s onset.

The social network says its new policy comes “in light of ongoing investigations into the origin”.

In February, Facebook explicitly banned the claim, as part of a broad policy update aimed at “removing more false claims about Covid-19 and vaccines”. In a public statement at the time, it said: “Following consultations with leading health organizations, including the World Health Organization (WHO), we are expanding the list of false claims we will remove to include additional debunked claims about the coronavirus and vaccines.”

Anyone posting claims that Covid-19 was “man-made or manufactured” could have seen their posts removed or restricted, and repeatedly sharing the allegation could have led to a ban from the site entirely.

On Wednesday, the company said: “In light of ongoing investigations into the origin of Covid-19 and in consultation with public health experts, we will no longer remove the claim that Covid-19 is man-made from our apps. We’re continuing to work with health experts to keep pace with the evolving nature of the pandemic and regularly update our policies as new facts and trends emerge.”

The change follows a Wall Street Journal report that US intelligence sources believe there is some evidence to warrant further investigation of the “lab leak” theory. According to the newspaper, three staff members at the Wuhan Institute for Virology sought hospital treatment for flu-like symptoms in November 2019. Others have criticised the reporting, noting that it still relies on circumstantial evidence and speculation.

Facebook is keen to ensure that a change in one rule doesn’t lead to a free-for-all for Covid misinformation. On the same day that it lifted the ban on lab-leak theories, it tightened up restrictions on users who “repeatedly share misinformation on Facebook”.

Under the new rules, individual Facebook users who repeatedly share content that has been rated false will have all their posts suppressed, even ones that have not been – or have yet to be – rated false. Additionally, users who like a page that has repeatedly shared false information will now be given a pop-up notice, warning them of the posting history.

“Whether it’s false or misleading content about Covid-19 and vaccines, climate change, elections or other topics, we’re making sure fewer people see misinformation on our apps,” Facebook said in a statement.

The company has come under fire this year for its failure to act on misinformation “superspreaders”: individual users with hundreds of thousands, or millions, of followers who regularly post false claims about Covid-19.