GENEVA (AP) — The World Health Organization says U.S. government-funded research on a deadly strain of bird flu has raised questions about the need for tighter safety measures to prevent scientific information from falling into the wrong hands.

The U.S. National Institutes of Health last week asked scientists at two universities to refrain from publishing full details of their work on how to make the H5N1 virus more easily transmissible between humans.

The unprecedented step by NIH prompted concern in the scientific community that researchers with a legitimate need to know about these dangerous mutations would be prevented from accessing the data.

WHO said Friday that the incident highlighted the existence of a "gray zone" in the way sensitive scientific information is handled.