NEW YORK – The worried manager of an industrial-sized pig farm in the little Mexican town of Xaltepec invited in journalists in an effort to calm things down.

"What happened was an unfortunate coincidence," he told them insistently. More than 3000km away in New York, the world's richest "pig baron", Joseph Luter III, is hoping he is right.

Downwind of Xaltepec - where 15,000 squealing hogs are squeezed into 18 warehouses - residents of La Gloria blame Smithfield, Luter's firm, for an outbreak of respiratory problems that swept the town last month, killing two children.

Now, with Mexican authorities identifying a 4-year-old from the town, Edgar Hernandes, as one of the first known cases of swine flu, furious residents believe they are ground zero of the flu alert.

The very suggestion has sent a shudder through the ranks of campaigners who have long argued that the sort of industrialised pig farming that has turned Smithfield into one of the most powerful corporations in the United States, with a market value of US$1.4 billion ($2.5 billion), was a disaster waiting to happen.

For Smithfield, the world's largest pork supplier, which processes more than one in three pigs killed in the US and jointly owns the Xaltepec plant and seven others in the region, the spiralling concern in Mexico threatens to become a worldwide marketing disaster - even before anyone is able to test the hunch of the people of La Gloria.

A team of United Nations veterinarians is arriving in Mexico to examine whether this new deadly strain of swine flu, mixed as it is with genetic material from avian and human strains, could be lurking in pig populations undetected. Smithfield says none of its pigs are sick but has sent samples for testing.

Victor Ochoa, the Xaltepec manager, ensured employees washed down cars coming into the plant yesterday and made journalists shower and don protective clothing before entering.

In common with his bosses back in the US, Ochoa insisted that all 15,000 animals had been properly vaccinated, that the plant met all the required health standards, and that the vast swimming pool of faeces - industrial pig farming's toxic byproduct - was covered with a lid to limit exposure to the outside air.

"What happened in La Gloria was an unfortunate coincidence with a big and serious problem that is happening now with this new flu virus," he said. La Gloria residents, though, have been protesting against the farm for months.

Starting in February, one in six of the 3000 residents reported health problems.

The Government initially dismissed the spike as a late-season rise in ordinary flu, but by April, health officials sealed off the town and sprayed chemicals to kill the flies that residents said were swarming about their homes.