Researchers in the Netherlands studying bird flu or avian influenza (H5N1) have reportedly developed a strain of the virus that's just as lethal as the original virus.

According to the New Scientist magazine, research on the bird flu virus has resulted in the highly contagious strain that has some scientists worried about the possible development of a bioweapon.

Media reports say the US biosecurity committee is deciding whether the crucial research is too dangerous to publish since it might allow the H5N1 to cause a lethal human pandemic.

The research was initially submitted to the journal Science, but has now been passed to the US National Science Advisory Board for Biosecurity (NSABB).

"The benefits of publishing this work do not outweigh the dangers of showing others how to replicate it," Thomas Ingelsby of the Center for Biosecurity was quoted as saying.

According to the US Department of Health & Human Services, the H5N1 kills more than half the people it infects, but cannot be readily passed from person to person.

It has so far infected more than 500 people in more than a dozen countries.

"The potential for escape of that virus is staggering," says D A Henderson of the Center for Biosecurity.

"A catastrophe would result" if a highly contagious virus with a 50 per cent kill rate got loose.

The NSABB does not have the power to prevent publication of scientific findings, but it can request that journals not publish certain studies.