TIANJIN • A senior Chinese official defended firefighters who initially hosed water on a blaze in a warehouse in north-east China where volatile chemicals were stored, a response foreign experts said could have contributed to two huge blasts that killed 54 people.

The police said that the warehouse, designed to house dangerous and toxic chemicals, stored mainly ammonium nitrate, potassium nitrate and calcium carbide. The official Xinhua news agency has said several containers in the warehouse caught fire before the explosions.

Chemical safety experts said calcium carbide reacts with water to create acetylene, a highly explosive gas. An explosion could be caused if firefighters sprayed the calcium carbide with water, they said.

Mr Lei Jinde, the deputy propaganda department head of China's fire department, told state-backed news website ThePaper.cn that the first group of firefighters on the scene had used water. "We knew there was calcium carbide inside but we didn't know whether it had already exploded," he said.

"At that point, no one knew, it wasn't that the firefighters were stupid," Mr Lei said, adding that it was a large warehouse and they did not know the exact location of the calcium carbide.

Mr David Leggett, a chemical safety expert based in California, said the acetylene explosion could have detonated the ammonium nitrate. The two blasts were about 30 seconds apart, with the second much larger than the first. "In my mind, the presence of ammonium nitrate makes it easier to explain the level of devastation," he said.

Dr Stuart Prescott, a senior lecturer in chemical engineering at the University of New South Wales in Australia, said water was recommended to extinguish the two nitrates but a chemical powder was needed for calcium carbide.

"Calcium carbide reacts with the water and that's a reasonably violent reaction in itself, because it releases gas. The gas itself is also flammable," he said.

REUTERS