(Xinhua)
Updated: 2007-09-18 16:42

Event organizers were illegally using highly combustible hydrogen in balloons that exploded, injuring more than 70 students at a Northwest China school on Sunday, according to local authorities.

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.

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.

If not stored or used properly, hydrogen gas could be dangerous, Yang said. Helium gas was encouraged for use in lighter-than-air balloons, but this was three to five times more expensive than hydrogen.

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 1,500 small balloons set to be released at the opening ceremony of a sports meeting unexpectedly exploded and caught fire at around 9:00 am on Sunday, injuring more than 70 students.

The balloons were provided by an event organizing company. Police are investigating the incident.