(A7) A Saturday blast at the Shahid Rajaee Port in Bandar Abbas, Iran, left 18 dead and around 750 injured, leading the Iranian government to declare three days of mourning.

The blast originated in containers at the port, reports said. Stored in the containers is a chemical used to make rocket fuel. Secondary explosions were reported.

By Sunday morning, hours later, firefighters were still working to extinguish the flames.

The port is expected to remain closed through Sunday.

According to reports, the explosion was felt in nearby cities, and shattered glass at sites kilometers away. State television added that a building collapsed due to the tremors.

Iran’s Customs Administration said that a “stockpile of hazardous goods and chemical materials stored in the port area” caused the explosion, IRNA said.

Ambrey, a private security firm, said that the port received a shipment of “sodium perchlorate rocket fuel” last month. “The fire was reportedly the result of improper handling of a shipment of solid fuel intended for use in Iranian ballistic missiles,” Ambrey said.

The investigation into the blast is ongoing.