Facebook has lifted a ban on posts that claim the coronavirus that causes COVID-19 was made by humans, amid renewed debate over its origins.

The reversal came as US President Joe Biden announced he ordered aides to find answers to the origin of the virus.

“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,” a Facebook spokeswoman said in an emailed statement.

“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 rule change came as US President Joe Biden announced he has ordered aides to find answers to the origin of the virus.

He said on Wednesday (local time) that US intelligence agencies are pursuing rival theories potentially including the possibility of a laboratory accident in China.

Social media companies have faced pressure to combat health misinformation on their sites during the pandemic.

Facebook has said it has removed more than 16 million pieces of content for breaking rules on COVID-19 and vaccine misinformation.

The company announced in February that it had expanded the types of claims it would remove from its platforms, including that the virus was made by humans.

It also banned the false notion that vaccines are not effective or that they are toxic.

Lisa Fazio, a professor of psychology at Vanderbilt University, said the reversal showed the difficulty of fact-checking in general, particularly with something unprecedented like the coronavirus, when experts can disagree and change their minds with new evidence.

“It’s one reason that content moderation shouldn’t be static, scientific consensus changes over time,” Professor Fazio said.

“It’s also a reminder to be humble and that for some questions the best current answer is “we don’t know yet” or “it’s possible, but experts think it’s unlikely”.

COVID-19 has killed more than 3.6 million people worldwide. The first reported cases emerged in the central Chinese city of Wuhan in late 2019 but the origin of the virus remains contested among experts.

Earlier this week, US government sources said a still-classified US intelligence report circulated during former president Donald Trump’s administration alleged that three researchers at China’s Wuhan Institute of Virology became so ill in November 2019 that they sought hospital care.

The source of that early intelligence or how reliable US agencies rate it is not known.

Facebook does not usually ban misinformation outright on its platform, instead adding fact checks by outside parties to debunked claims.

The two exceptions have been around elections and COVID-19.

-with agencies