GUANGZHOU -- Chinese epidemiologists have discovered that a mysterious pig epidemic spreading throughout south China's Guangdong province is an outbreak of an infectious disease commonly known as "blue ear disease".

The disease was first found in Silao town of Yunfu city at the end of April, after pigs stopped eating, developed fevers and started hemorrhaging. More than 300 pigs died.

The "blue ear disease" spread to China in the middle 1990s and the recent outbreak in Guangdong was caused by a deadly mutation of the virus. China has already developed effective vaccines for the disease and they will be used in Guangdong soon, said the provincial agriculture department.

According to Yunfu government, the infected pigs were raised by individual rural households rather than industrialized pig farms and were not exported to Hong Kong or overseas markets.

Major roads in and out of the town have been sterilized and the sale of pigs in the infected area has been banned.