From Wikipedia's account - <a href="https://en.wikipedia.org/wiki/SS_Morro_Castle_(1930)#Causes" rel="nofollow">https://en.wikipedia.org/wiki/SS_Morro_Castle_(1930)#Causes</a> - the cause of the fire could be (in effect) an overheated storage locker full of oily rags.
This took an interesting turn. A sprinkler system might have helped but it's not mentioned as part of the changes in maritime regulations following the incident.