LANZHOU, Sept. 22 (Xinhua) -- Balloon provider had illegally used highly combustible hydrogen in balloons that exploded last Sunday injuring nearly 100 students at a northwest China school, local authorities said on Saturday.
A local company that provided the balloons is responsible for the incident, according to the Gansu provincial Bureau of Work Safety. The firm filled the balloons with hydrogen instead of helium as required, resulting in the blast, when the students were holding a celebration event.
The use of hydrogen in balloons violated regulations passed by the central government, said Yang Yucheng, an official in charge of policy and regulations with the provincial Meteorological Bureau.
He said the handling and release of hydrogen-filled balloons required government permission. But the event organizers did not report their plan or check the balloons.
The number of hydrogen-filled balloons at any event was also strictly limited to 1,000, said Yang, citing a circular jointly released by the State Council and China Meteorological Administration in July 2006. But the number of the balloons used at the school event was about 1,600.
Hydrogen gas could be quite dangerous if it is improperly stored or used, Yang said. Helium gas, which is three to five times expensive than hydrogen, was encouraged for use in balloons.
The explosion in the Lanzhou Electric Power School in the Anning District of Lanzhou, capital of Gansu, could have been caused by static electricity, Yang said.
About 1,600 small balloons set to be released at the opening ceremony of a sports meeting unexpectedly exploded and caught fire at around 9:00 a.m. on Sunday, injuring 98 students.
Police are carrying out further investigation into the incident.