Examining possible cause of the Napa County Pickett Fire

The NBC Bay Area Investigative Unit has learned of a possible cause of a wildfire in Napa County.

The Pickett Fire broke out Thursday afternoon along Pickett Road, just north of Calistoga near Hundred Acre Winery. The blaze has burned over 6,800 acres and is 25% contained.

Cal Fire has been suspicious of the cause from the start because the burn zone is in such a remote area. But NBC Bay Area has learned Cal Fire investigators now suspect it sparked when a contract worker at a vineyard apparently discarded ashes improperly.

Investigative Reporter Jaxon Van Derbeken has more in the video above.