A week after wind-whipped wildfires began their deadly rampage through Southern California, details on acreage burned, structures destroyed and people killed are routinely updated on a state website devoted to tracking the devastation.

But one category regarding each fire remains unchanged: The cause.

Amid speculation, rumors and media reports regarding how the fires may have begun, the official determination for each blaze is “under investigation.” Fire experts and arson investigators interviewed by  said it could take weeks, months or even longer before they know precisely how the fires ignited.