South Korean quarantine authorities said Wednesday they have confirmed the fourth outbreak of bird flu in the the country this year.

The Ministry for Food, Agriculture, Forestry and Fisheries said the "H5 type" of avian influenza was found at a duck farm in the Youngwon-myeon area of the city of Jeongeup. The city in North Jeolla Province is located 271 kilometers south of Seoul.

"More detailed tests have to be run, but judging by the number of sudden deaths, experts are certain the ducks died from the virulent strain," said a government official.

Quarantine authorities have already confirmed that the first reported outbreak at a chicken farm in Gimje, 27 kilometers north of Jeongeup, was caused by the highly contagiously H5N1 strain that has previously affected humans.

It also said Monday that bird flu was confirmed at another duck farm in Youngwon-myeon and at a poultry farm in nearby Gobu-myeon.

The areas of the two outbreaks in Youngwon are only 2.7 kilometers apart. The ministry added the second farm hit by bird flu in Youngwon is about 3 kilometers from the Gobu duck farm.

"As a precautionary measure, all of the poultry at the nine poultry farms located within 3 kilometers of the first outbreaks in Youngwon and Gobu have been culled and buried," said a local official. A total of 150,000 were culled, and quarantine officials are ready to cull more if necessary.

Under standing operational procedures, all movement of birds, people and vehicles are strictly controlled within a 10 kilometer radius of all outbreaks. The quarantine is usually maintained for three weeks, the maximum incubation period for bird flu.

Authorities are currently conducting tests taken on samples from 10 other poultry farms in North Jeolla Province to see if they have been affected by avian influenza.

The ministry, meanwhile, said it has culled a total of 524,00 birds so far and destroyed 23.3 million eggs. The losses are expected to total 7.5 billion won ($7.6 million).

South Korea has been hit twice before by the disease, once in the winter of 2003-2004 and once in 2006-2007, resulting in considerable loss of property and a sudden drop in demand for poultry.