A federal government agency in the United States has asked two scientific journals not to reveal how to make a deadly version of a bird flu virus.
Science and Nature are due to publish details of the research in a Dutch laboratory, where a highly contagious version of the H5N1 virus was created.
The BBC reports the papers show how a bird flu variant can pass easily between ferrets.
While bird flu is deadly, its reach has been limited because it is not transmissible between humans.
However, the flu virus was altered in the new studies to be passed easily between ferrets.
In a statement on Tuesday, the National Science Advisory Board for Biosecurity said the mutations mean the flu would have "greater potential" to be contagious among humans.
Editors at the journals say they will not agree to the editorial changes requested by the board, until they are assured the data will be accessible to researchers.
The BBC reports the recommendation is unprecedented for the board, which was created after anthrax attacks in 2001.
The Department of Health and Human Services said it agreed with the board's recommendation.