TOKYO, Sept. 10 (Xinhua) -- After confirming the outbreak of swine flu at a farm in Gifu Prefecture, central Japan, authorities said Monday that 546 hogs had been culled and buried, and pork exports from across Japan had been halted to contain the spread of the virus.

At the farm in Gifu, local media reported that 140 pigs had died over the past week due to the disease which is also known as hog cholera.

Until last Wednesday, the farm had been shipping pork. This was two days after a pig was suddenly found dead there, but did not test positive for the disease after a preliminary screening.

It was not until Sunday that further tests by the government showed the pig had contracted the virus.

The disinfection of the farm will be completed by Tuesday, officials said, although it remains unclear how the outbreak started.

The local government in Gifu suggested the virus may have made its way onto the farm by way of wild boars or pigs that had contracted the disease and had been brought onto the farm.

No infections of pig cholera have been recorded in Japan since the first outbreak in 1992 and the virus was declared eradicated in 2007, according to official records.

Shipment of pigs from facilities within a 10-km radius of the infected farm have been prohibited to prevent the virus from spreading and five disinfection zones have been set up to clean vehicles that carry livestock in the area, local officials said.

The shipment ban will likely be in place for a minimum of three months until the virus is officially declared as having been eradicated.

Following the shipping ban, Japan's export of pork products can continue to countries that give their approval.