HARBIN - Four people were seriously injured in a disinfectant factory blast Friday morning in Northeast China's Heilongjiang province, said local officials.

The four injured, one woman and three men, were still in critical condition Friday afternoon, according to doctors with No 5 People's Hospital in the provincial capital Harbin.

At least 95 percent of their bodies were burned. They were also suffering from serious smoke inhalation injuries, the doctors said.

The disinfectant factory in Xiangfang district is privately owned, said Sun Hengyi, deputy secretary of the district's committee of the Communist Party of China.

Police have cordoned off the factory. An investigation team have been formed to find the reasons for the blast, Sun said.

Residents living near the factory have been evacuated.