9 firemen are killed.
Witnesses described a "tornado of flames" as the roof of the building collapsed.
Up to 24 firefighters were inside the factory in Charleston, South Carolina, at the time.
They were showered with burning debris when a 30ft ball of fire shot over their heads.
Several men leapt through ground floor windows to escape while two staff ran to safety.
It is the single biggest loss of life for the fire service since 9/11.