KUNMING, March 14 (Xinhua) -- Ten students were injured in an explosive blast on Wednesday morning in a junior high school in southwest China's Yunnan Province, local police said.

Police investigation found that the blast occurred when two students were examining a device in Dongfeng School in Mile County of Honghe Hani and Yi Nationalities Autonomous Prefecture, according to a spokesman of the local Public Security Bureau.

Student Wang Zhenping brought the device from home to the classroom and showed it to his classmate Wang Hai, who accidentally let it off, police said. The students are in their first year in junior high school.

Ten of the 49 students in the class were injured. Two who have suffered serious injuries were sent to Mile People's Hospital while the other eight were treated in Dongfeng Hospital, the spokesman said.

Police have initially identified the device as a grenade and they are investigating where it came from and how the student got it.