We had an arsonist in my town (in the foothills of the Sierra Nevada Mtns) a couple of years ago. When they finally caught him he had "fire making materials" that matched evidence found at the scene of several fires. He used the old "cigarette in a book of matches" trick, they found matching books of matches, same brand of cigs, etc. I can only assume that is what they are refering to in this case.

Our guy turned out to be a former volunteer firefighter, which apparently is not all that uncommon...