Investigations are under way after a mysterious disease killed 17 farm workers and left at least 12 in a critical condition in hospital in Southwest China's Sichuan Province.

　　Zeng Huajin, a senior official with the provincial health department, said the deadly illness was "probably" caused by streptococcus suis, a bacteria usually spread among pigs.

　　An initial 20 farm workers who handled sick or dead pigs and sheep in 12 towns and 15 villages in Jianyang city and Ziyang city's Yanjiang district suffered from high fever, nausea, vomiting and haemorrhaging. Zeng said the disease could not spread among humans, and normally only those with a weak immune system became ill.

　　The Ministry of Health and Ministry of Agriculture last week sent a special team to Sichuan to assist in the investigation, treatment and control of the outbreak.