Any polymerization reaction is likely to be exothermic, and with the heat contained as well as it is by fine dust or a tightly twisted rag, stuff can happen. You're not safe because it's not linseed.
I'd let any finish cure well before sanding, even a "sanding sealer," which is normally a thinned version of a finish.
Linseed oil is notorious for combustion, maybe you had some of that in there.