Residents here believe their town is ground zero for the swine flu epidemic, even if health officials aren't saying so. More than 450 members of this community say they're suffering respiratory problems from contamination spread by pig waste at nearby breeding farms partly owned by a U.S. company.

As far back as late March, roughly one-sixth of the members of this community of 3,000 in the Gulf coast state of Veracruz began suffering from severe respiratory infections that they directly trace to a farm that lies upwind five miles (8.5 kilometers) to the north, in the town of Xaltepec.

Mexican officials say they haven't determined the origin of the country's swine flu outbreak, which has caused at least 20 deaths so far.

But Jose Luis Martinez, a 34-year-old resident of La Gloria, said he knew the minute he heard about the outbreak on the news, with symptoms including a fever, coughing, joint aches, severe headache and, in some cases, vomiting and diarrhea.

"When we saw it on the television, we said to ourselves, 'This is what we had,'" he said Monday. "It all came from here. ... The symptoms they are suffering are the same that we had here."

Martinez and Bertha Crisostomo, a liaison between the villagers and the municipal government of Perote to which La Gloria belongs, say half of the people from the town live and work in Mexico City most of the week, and could easily have spread the swine flu in the capital, where the largest number of cases have been reported.

Granjas Carroll de Mexico, 50 percent owned by Virginia-based Smithfield Foods, Inc., has eight farms in the area. Smithfield spokeswoman Keira Ullrich said the company has found no clinical signs or symptoms of the presence of swine influenza in its swine herd or its employees working at its joint ventures anywhere in Mexico.

Residents say they have been bothered for years by the fetid smell of one the farms which lies upwind of the community and suspect their water and air has been contaminated by waste.

When an Associated Press team entered the farm on Monday, cars were sprayed with water. Manager Victor Ochoa required the visitors to shower and don white overalls, rubber boots and masks before entering any of the 18 warehouses where 15,000 pigs are kept.

Ochoa showed the journalists that a black plastic lid covered a swimming pool-size cement container of pig feces, to prevent exposure to the outside air.

"All of our pigs have been adequately vaccinated and they are all taken care of according to current sanitation rules," Ochoa asserted. "What happened in La Gloria was an unfortunate coincidence with a big and serious problem that is happening now with this new flu virus."

Martinez said residents have been fighting for years to force the company to improve their pig-waste management. Mexican news media reported that a municipal health official traced the source of a disease outbreak in La Gloria to a type of fly that reproduces in pig waste.

Local health officials and Federal Health Secretary Jose Angel Cordova downplayed claims that the swine flu epidemic could have started in la Gloria, noting that of 30 mucous samples taken from victims of respiratory diseases there, only one _ that of 4-year-old Edgar Hernandez _ came back positive. The boy later recovered.

Cordova insisted the rest of the community had suffered from a common influenza.

Mexican Agriculture Department officials said Monday that its inspectors found no sign of swine flu among pigs around the farm in Veracruz, and that no infected pigs have been found yet anywhere in Mexico. However, the inspections may have been less than complete: Ochoa, the farm manager, said no one from the government has inspected his farm for swine flu.

Juan Lubroth, an animal health expert at the U.N. Food and Agriculture Organization in Rome, supported officials' assessment of the pig situation and said there is no evidence of sick or dying swine in Mexico.

Lubroth noted that Mexico has a surveillance system that previously eliminated an unrelated disease from the country's commercial pig population, which he said is a good indication that they also are conducting adequate reviews of pigs for swine flu.

Dr. Alejandro Escobar Mesa, deputy director for the control and prevention of disease for the state of Veracruz, said the epidemic in La Gloria was a combination of viral and bacterial illnesses, caused by an unusually dry climate.

"The dust dries up the mucous membranes and facilitates environmental conditions for the transmission of illnesses," Escobar said.

But residents here say they are certain that Edgar Hernandez was not the only swine flu victim in their town.

Concepcion Llorente, a first-grade teacher in La Gloria, says authorities still owe the town some answers.

"They said that what we had here was an atypical flu, but if the boy tested positive for swine flu, where did he get it from?"

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AP Medical Writer Margie Mason and AP writers Mark Stevenson and Lisa J. Adams in Mexico City contributed to this report.