A U.S. biosecurity agency says it asked two scientific journals to censor the publication of research on a flu virus for safety reasons.

The US National Science Advisory Board for Biosecurity made the request to the journals Nature and Science to redact the publication of two papers by research teams who modified avian H5N1 influenza strains to create mutant viruses that can be transmitted efficiently between mammals.

The board, in a statement released Tuesday, said it concluded publishing the work in full would provide information that might allow some persons, organizations or governments to develop similar mammal-adapted influenza viruses for harmful purposes.

"A pandemic, or the deliberate release of a transmissible highly pathogenic influenza A/H5N1 virus, would be an unimaginable catastrophe for which the world is currently inadequately prepared," the NSABB said in its comment.

The NSABB did acknowledge the research holds "clear benefits" and could lead to greater preparedness and potential development of new strategies for disease control.

By recommending the basic results be communicated without methods or details, it said, the benefits to society would be maximized and the risks minimized.