Since late January, Chinese researchers have published a series of Covid-19 studies in influential international medical journals. Some findings about early coronavirus cases — such as when human-to-human transition first appeared — have raised questions over the official government account of the outbreak and sparked controversy on Chinese social media.

And now, Chinese authorities appear to be tightening their grip on the publication of Covid-19 research.

A Chinese researcher who spoke on condition of anonymity due to fear of retaliation said the move was a worrying development that would likely obstruct important scientific research.

“I think it is a coordinated effort from (the) Chinese government to control (the) narrative, and paint it as if the outbreak did not originate in China,” the researcher told CNN. “And I don’t think they will really tolerate any objective study to investigate the origination of this disease.”