An official from China’s State Administration of Work Safety says that the cause of the Tianjin blast on Wednesday is still pending, because the fire at the scene has not been completely put out, according to Xinhua.

“Only after the fire is totally put out can we find out the exact place where the fire started, and subsequently the cause of the explosion will be figured out,” Xinhua quoted him as saying, but failed to identify him.

Blasts tore through a warehouse in Tianjin's port area in north China on Wednesday night. As of Thursday night, the blasts have killed 50 people, 12 of whom were firemen. Another 701 people are still in hospital, many gravely ill.

Emergency personnel are continuing the search for the missing firefighters, but this is already one of the biggest losses of firemen in the line of duty for decades. Of the hundreds injured who mostly suffer from burns or broken bones, 71 are in critical condition.