Comment: Ok

Just watched that entire video. There isn't one even still frame of molten steel, or even any video of molten steel at all. Incandescent steel is one thing, molten is another. Molten metal is not the same as steel, and at a guess no one took samples of any actual molten metal and ran an analysis of composition on them.

Fire, fires and extreme heat can get trapped under ground, and when exposed to oxygen they can ignite, I don't see anything super unusual in that from a science basis.

Molten metal is to be expected, I'm looking for video of actual melted steel. Although this video does show proof that the steel was never vaporized or dustified or whatever. Look at those huge piles.

Eric Hoffer