Vietnam requested the help of the FAO after reporting an outbreak of deadly "blue ear" pig disease in four provinces in recent months, amid fears the animal virus might have travelled south from neighboring China.

An expert team from the FAO and World Organisation for Animal Health (OIE) has visited Vietnam and sent samples to a US laboratory for sequencing of the viral strain and to identify a vaccine, said the FAO in a statement.

The team, which reported its findings to Vietnam's communist government Tuesday, said "it appears that there are a number of swine diseases that may be interacting to cause the unusual signs being observed."