According to the Ministry of Agriculture and Forestry Tuesday, South Korea has tightened quarantine measures for travelers returning from abroad after a renewed outbreak of bird flu hit a poultry farm in the central part of the country, killing 3,500 chickens.

Kim Chang-seob, chief of the ministry's animal health division, said that, since bird flu had recurred in the province where South Korea's first outbreak was originally reported and Southeast Asian countries have reported confirmed cases, the government would adopt strengthened quarantine measures for those returning from abroad.

Kim said in cooperation with the Korea Customs Service and other relevant ministries, the agriculture ministry has increased the number of quarantine officials at ports of entry and established more quarantine centers.

On Monday, the ministry confirmed the nation's first outbreak of avian flu in 13 days, increasing the number of confirmed cases at farms to 17 since the first one on Dec. 15 in North Chungcheong Province, the local epicenter of the sickness.

Authorities started an investigation on Sunday after a farmer in Cheonan, about 92 kilometers south of Seoul, reported that 3,500 chickens at the farm were suspected of dying from avian flu, also known as the H5N1 virus.