Officials in China now say at least 56 people were killed in powerful explosions in the port city of Tianjin Wednesday. More than 700 injured are being treated at hospitals. It is not known how many other people may be missing.

Chinese investigators are trying to learn what caused the explosions. They took place at a building that holds chemicals. Safety officials in Tianjin said they do not know what kinds of chemicals were stored in the building. China’s officials Xinhua news agency says a team of 217 experts has been sent to the area.