LINGAYEN, Pangasinan, Philippines—Teams from three United Nations agencies on Thursday started investigating cases of Ebola-Reston virus infection of hogs in pig farms in Pangasinan and Bulacan.

The teams are composed of animal and human health experts from the UN's Food and Agriculture Organization, World Organization for Animal Health and World Health Organization.

In Pangasinan, William White, senior staff veterinarian of the United States Department of Agriculture, said his team would "examine in detail" the affected farms in the province.

Dr. Reildrin Morales, head of the field operations group of the Bureau of Animal Industry, said the experts would visit the farms in Manaoag town to collect samples and to assess if the virus is still present there.

"There will be a series of field investigations; there will be sample collections," he said.

Another pig farm in Pandi, Bulacan, had been found positive for the Ebola-Reston virus, which, experts said, was being detected for the first time in hogs in the country.

The virus was first detected in 1989 in laboratory monkeys sent from the Philippines to Reston, Virginia, in the United States.

Boris Pavlin, a WHO epidemiologist, said the virus did not pose any threat to humans.

"Even if we found somebody positive, it's very unlikely that he could spread the virus anywhere else. So, we do not feel that there's any ongoing danger [of] the virus being spread [to] the human population as of this time," Pavlin said.

In a joint statement distributed to reporters, the departments of agriculture and health said the presence of the Ebola-Reston virus in the country is "predominantly an animal health issue."

"The Ebola-Reston virus is one of five Ebola strains, but has no significant risk to humans," it said.

It said that since the virus was found in local pigs in October, the DA and the DOH have been conducting laboratory tests on blood and tissue samples collected from pigs and animal handlers from affected farms and slaughterhouses.

"All of the samples yielded negative," it said.

Morales said they could not tell yet the symptoms in an Ebola-Reston virus-affected pig, saying the samples they submitted to the US for testing was not for the virus.

"Ebola is an incidental finding. We do not know how it behaves. We do not know the time frame that it might give to the animals. We do not know if at all it shows medical signs in a pig," he said.

White said the pigs were being investigated for a "very severe disease" called porcine reproductive and respiratory syndrome, which is caused by a virus.

"Coincidentally, we came across Ebola-Reston. It's there but we do not know what it means," White said.

The UN team will work with Filipino counterparts for 10 days.

In Bulacan, Felipe Bartolome, provincial veterinary officer, said the experts would start gathering tissue samples at the Win Farm in the village of Sto. Niño in Pandi town on Friday.

Earlier, Bulacan hog raisers assured that pork from the province was safe and there was no cause for alarm.

Lito Hizon, president of Livestock Raisers Association in Pandi, said it was only in one farm where the virus was detected.

He said the DA ordered a quarantine and strict monitoring at the farm last month.

Bulacan, according to records of the provincial agriculture office, is among the major suppliers of pork to Metro Manila.

Aside from Pandi, the towns of Sta. Maria, Bustos, San Miguel and Baliuag and San Jose del Monte City are the top hog raisers in the province.