WUHAN, May 21  -- The man who injured eight pupils in a knife attack in a school in central China's Hubei Province on Tuesday has tested positive for methamphetamine in a urine drug test, local police said.

According to the investigation, 35-year-old Chen Zuihang used drugs and showed abnormal behavior before the stabbing spree in Macheng City.

He has a history of drug use, and was detained by his hometown police in Luoyuan County of east China's Fujian Province for drug use in 2006 and 2011, the police said.

The migrant worker rushed into the Wulidun elementary school carrying a kitchen knife at around 12:19 p.m. on Tuesday and started to attack students, according to the Macheng government.

Li Jianxin, a school teacher, said teachers caught the suspect at the scene and called the police. The injured, all from the first and second classes, were hospitalized. One student suffered serious injuries, while the other seven had minor injuries.

"An eight-year-old boy had suffered massive blood loss by the time he was sent to our hospital," said Huang Dan, a doctor in the city's People's Hospital.

Huang said the boy is still in critical condition and needs further observation in the intensive care unit.

The local government said the school head has been suspended and the person in charge of school security has been sacked. Further investigation is under way.