BEIJING, Dec. 24 -- Chinese authorities are focusing on the liability of Shenzhen drug manufacturer BioKangtai whose vaccines have been associated with eight infant deaths since November.

Four of the babies who died were from south China's Guangdong Province, two from central China's Hunan Province and two from Sichuan Province in southwest China.

"Inspectors are investigating production procedure and materials used to produce hepatitis B vaccines," said Li Guoqing, head of inspections at the China Food and Drug Administration. On Dec. 13, Li sent an investigation team to Hunan where three children displayed adverse reactions after receiving BioKangtai vaccines.

Local food and drug supervisors in Hunan and Guangdong have randomly sampled BioKangtai vaccines, Li said, adding that the administration has suspended use of the suspected vaccines.

The investigation will take about 20 days and supervisory departments will make the results public in a timely manner, he added.