Cause of Tianjin explosion still under investigation

At least 56 dead, including 21 firefighters, reported in the aftermath of Wednesday’s explosion in the northern Chinese port.    The death toll from an explosion in the Chinese port city of Tianjin late Wednesday night has risen to 56, including 21 firemen, according to the state-run newspaper People’s Daily.
   The newspaper said the dead firefighters were among those trying to extinguish a blaze prior to two massive warehouse explosions.
   There was also widespread property damage. People’s Daily said almost 10,000 new cars were ruined.
   The cause of the explosion is still under investigation, but there are some reports that a mix of chemicals stored in the warehouse could have been a contributing factor.
   Reuters said police reported the warehouse was “storing mainly ammonium nitrate, potassium nitrate and calcium carbide” and the news agency Xinhua said several containers in the warehouse caught fire before the explosions.
   Reuters also said chemical safety experts told the news service that calcium carbide reacts with water to create acetylene, a highly explosive gas and that an explosion could be caused if fire fighters sprayed the calcium carbide with water. It was not clear if the calcium carbide was already burning before the firefighting began.
   David Leggett, a chemical safety expert based in California, told Reuters that an acetylene explosion could have detonated the ammonium nitrate. Two blasts Wednesday night were about 30 seconds apart, the second much larger than the first.