Almost four thousand people are injured and more than 70 dead after a huge explosion in Beirut, Lebanon Tuesday (watch above via Sky News). The death toll is expected to rise significantly as rescue workers comb through the debris.

NBC quotes Beirut’s Mayor as saying “It’s like Hiroshima… There is lots of destruction and the wounded are lying in the streets.”

The explosion, which was said to be felt throughout the city, collapsed buildings and sent debris flying. There were early reports that the explosion was related to fireworks, but that was quickly discounted. The AP reports:

Abbas Ibrahim, chief of Lebanese General Security, said it might have been caused by highly explosive material that was confiscated from a ship some time ago and stored at the port. Local television channel LBC said the material was sodium nitrate.

Witnesses reported seeing a strange orange-colored cloud over the site after the explosion. Orange clouds of toxic nitrogen dioxide gas often accompany an explosion involving nitrates.

Even before this, Lebanon was already in the middle of several crises.