Lanzhou Veterinary Research Institute of the Chinese Academy of Agricultural Sciences. (File photo: Chinanews.com)

More than 6,600 people in Lanzhou, capital of Northwest China's Gansu province, have tested positive for a bacteria that could cause Mediterranean fever following an accident in a vaccine production factory last year, the city government said on Thursday.

Meanwhile, eight employees at the factory have been held accountable and received punishment including warning and removal from their posts.

The infections were caused by the use of expired disinfectant at the factory, a branch of China Animal Husbandry Industry Co, in Lanzhou in the production of animal vaccines between July 24 and Aug 20 last year, the city authorities said. This resulted in the brucella bacteria entering the exhaust emitted by the factory, which infected students and faculty at Lanzhou Veterinary Research Institute of the Chinese Academy of Agricultural Sciences, which is near the factory, and others in nearby places.

The factory closed the workshop for the production of the vaccines for brucellosis, also known as the Mediterranean fever, on Dec 7, and tore down the workshop in October this year. The Chinese Center for Disease Control and Prevention and the provincial CDC have conducted sampling tests in areas surrounding the factory and no brucella bacteria was detected, Lanzhou government said.

So far the city authorities have conducted test over 55,725 people, and 6,620 of them have tested positive for the virus.

The city has provided free treatment to all who tested positive and showed symptoms, and 126 patients had received treatment at 11 hospitals in Lanzhou, the city's health commission said.

China Animal Husbandry Industry Co has allocated 10 million yuan ($1.5 million) to pay for the diagnosis and treatment, and compensation for the affected people, and has pledged to add more money if required for compensation, according to Lanzhou's agriculture and rural affairs bureau.