When these high speed mostly fully automated lines are flowing properly there are very few if any workers near them to shut them down in event of a problem. Even if someone had their hand on the kill switch and shut down the machine the instant a problem developed machines cannot stop instantly. Who knows how many furnaces and extruding mills that string of steel has already gone through from ingot to wire.
My concern is the aftermath, I'd be worried about the amount of concentrated heat on that Bar joist type truss. Is it enough to weaken it to the point it can no longer be considered safe. The roof was glowing red makes me think there is damage above as well.