South Korea has declared an area hit by toxic chemical leak a special disaster zone to clear the way for state assistance to residents there.

Eight tons of hydrofluoric acid leaked after an explosion last month at a chemical factory in the southeastern city of Gumi that initially killed five people.

Gumi officials say about 4,260 residents have received medical treatment and check-ups after being exposed to the toxic gas and about 300 others have been evacuated to city-run facilities.

About 3,200 cows, goats and other livestock have been affected by the chemical leak.

The Prime Minister's office said Tuesday the disaster zone designation enables the government to provide financial and administrative assistance to the stricken area.