Health authorities in Taicang, Jiangsu province, are investigating the case of a 2-year-old boy who died after being vaccinated against hepatitis A earlier this month.

On Dec 6, the boy from Yongjia, Zhejiang province, received his second injection of hepatitis A vaccine at Taicang Chengxiang Town Community Health Center. But the next day, the boy reportedly became pale, and his lips turned blue. He died shortly after being taken to the hospital, according to Modern Express.

The Taicang health bureau announced the death on Thursday, saying it has started an investigation.

The local police department said it will perform an autopsy to try to discover the cause of the boy's death.