The 51-year-old man probably died from heart problems, said Public Health Deputy Permanent Secretary Dr Somyos Charoensak.

The ministry's investigation unit had gone straight to the ves?sel that carried the corpse of the man back from Indonesia as soon as it anchored at a port in Samut Prakan's Phra Pradaeng, said Somyos.

The preliminary investigation showed the man, who worked as a welder for a Vietnamese commer?cial boat hired by a Thai company to transport goods between Thailand and Indonesia, had not been in contact with any sick poul?try and did not have a fever before he died on the way back to Thailand, he said.

Before he died suddenly on January 14 while at sea, the man reportedly suffered severe fatigue and wheezing - indicating symp?toms of heart disease, said

Somyos.

Moreover, as a welder, the man didn't leave the vessel while it was anchored in Indonesia, he said.

"Regarding his history and symptoms, this is not bird flu," Somyos said, adding that the autopsy results were expected to be known within a week.

The remaining 24 crew mem?bers travelling with the man were all in good health.

In Phitsanulok, where H5N1 infections were recently confirmed in free-range ducks, health officers continued to monitor the situation closely and no case of suspected bird flu had been detected so far, said Somyos.

The lab results of two patients, a 29-year-old man and 13-year-old boy from the same sub-district where the bird-flu infected ducks were found, confirmed they had human influenza - not bird flu, he said.

The Nation