One pupil had undergone an emergency operation and none of them was in critical condition.

The explosion occurred at about 1 pm on the fourth floor of a teaching building of Daxuelu Primary School, and all 12 injured pupils were immediately sent to the hospital.

The explosion was caused by a pupil surnamed Feng, 13, who brought the detonating fuse of an old cannonball to the school and played with it in the corridor of the building, which drew many other curious playmates.

Feng became excited and threw the fuse to the ceiling, which caused the blast.

Leaders of both Zhejiang Province and Hangzhou City and officials of the relevant departments rushed to the accident scene to investigate. Everything soon returned normal at the school, and classes had resumed normal operation later in the afternoon.

The cause of the accident is under further investigation.

(Xinhua News Agency March 31, 2003)