I remember decades ago in a town i grew up in in northern Michigan, there was a tannery on the shore of Lake Charlevoix and a dock where the coal freighters would unload the coal for the tannery.
If not used on a regular basis, the piled up coal would start to spontaneously combust in the center of the pile and start smoking. To get around that, they would frequently bulldoze the piles to prevent the build up of heat.
Fires in coal piles at utilities are fairly common and one of the reasons only a week or so supply is on hand. The piles are constantly turned to avoid them getting out of control. Not sure how much coal was necessary to power Titantic, but it must have been a substantial pile.
If not used on a regular basis, the piled up coal would start to spontaneously combust in the center of the pile and start smoking.
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I’ve heard the same about piles of oily rags and leaves, too. I think any big pile of organic material can smolder.