The UN Food and Agriculture Organisation says there is no evidence of avian flu in pigs, dismissing an earlier report.
An FAO spokesman in Hanoi had earlier said that the bird flu virus had been found in the nasal cavities of several Vietnamese pigs, but a FAO scientist in Rome said the tests he had referred to were not up to standard.
The FAO is investigating the exact origin of the earlier report, a potentially disastrous development in the avian flu crisis.
Pigs have a similar immune system to humans and suffer from a wide variety of diseases that also infect people.
Two more people died of the virus in Vietnam today, bringing the total so far to 18.
Fifty million birds have been culled in Asia so far and it is estimated that poultry restocking alone will cost almost €190m.
