The American government advisory board took the extra-ordinary step after scientists, experimenting in the US and Netherlands, created a highly transmissible form of deadly flu virus that does not normally spread from person to person.
The experiments, the New York Times reported, where done in ferrets, which are considered a good model for predicting what flu viruses will do in people.
The virus A(H5N1) causes bird flu which rarely infects people but has an extra-ordinarily high death rates when it does. Since the virus was first detected in 1997, about 600 people have contracted it and more than half have died.
Most of the case, the paper said, had been in Asia and scientists have monitored the virus, worrying that if it developed the ability to spread easily from person to person it could create one of the deadliest pandemics ever.
The NYT said that the government panel had asked the two journals Science and Nature to keep certain details out of reports that they intended to publish.
"Experimental details and mutation data that would enable replications of the experiments" should not be published, the panel has directed.
Ever since, the tightening of security after the 9/11 terror attacks, scientists have worried that the scientific development would pit the need for safety against the need to share information.
Now it seems that day has come, the NYT quoted US officials as saying.