We don’t know for sure what caused the explosion. The news states that when it occurred, the engineer was pumping water into the boiler. It also states that the boiler was overheated. Many conditions could have occurred that brought on this event. The news states all the lumbermen were huddled underneath the boiler room while a fierce storm passed over just before it happened. I have the news articles and a supporting document showing the weather report of the area on that day.

This shows an average temperature of 92 degrees with threatening showers.

Most likely, after the storm calmed, the news articles state that the engineer Joe Turner started pumping water back into the boiler.  It has been said that at that time lightning also struck the boiler. There is also the possibility that if the boiler got wet from the rain that it would have caused the explosion. These suggested causes cannot be confirmed but, due to the storm conditions of that day, any of these conditions were possible. 

background photo courtesy Roxie Hampton Roger’s private collection. Little River Lumber Company, Elkmont, Tennessee located some 20 miles from T J Salts Lumber Company in Dry Fork Tennessee. Second man is Blackie Hampton

Above reference from “Insurance Engineering”, Volume XI, January - June 1906 - “Effect of Low Water”