An 18-member team of experts from the United Nations' Food and Agriculture Organisation, the World Health Organisation and the World Organisation for Animal Health arrived in Manila on Monday to help the government investigate the virus.

The 10-day mission will focus on the source of the virus, how it is transmitted, its virulence and the best way to identify it, the experts said.

The Ebola Reston strain was found last October in tissue samples tested in the United States from six pigs from farms in the northern Philippines.

This not only marked the first time the virus has been discovered outside monkeys, but also the first time it has been found in a food-producing animal.

As a precaution, the Philippine authorities stopped a shipment of 50,000kg of frozen pork to Singapore late last year.

Unlike the deadly strains of the Ebola virus, the Reston strain has never been found to cause major illness or death in humans.

'We have no evidence that there is a risk, but our contention is that a lot more work needs to be done before we can be sure,' said an official with one of the international health organisations.