A total of 13 people have tested positive for brucellosis antibodies in northeast China's Heilongjiang Province, local health commission said on its official website on Tuesday.

The development comes after 96 people were confirmed having the same disease in northwest China's Lanzhou Veterinary Research Institute (LVRI) last week.

"Experts have determined that the bacteria were imported," the commission said.

All the 13 patients were studying at LVRI in August, where they came into contact with animals, and they had no animal contact in Heilongjiang, the statement added.

However, the exact source of the disease has not been identified and the deputy governor of Gansu has ordered officials in Lanzhou to carry out an investigation. 

Brucellosis, also known as Mediterranean fever, is an infectious bacterial disease that spreads from animals to people. The disease is treatable and does not spread from people-to-people contact.