According to the story below, a leader of the Santa Muerte sect "took his followers to Los Angeles National Forest for a ceremony by the river, with incense burning and chanting."
Video of the river is shown at around 1:55 in the video. I'm not good at recognizing areas, but I imagine it's car-accessible. Thankfully it's incense they're burning and not anything sinister (cf. Curve Fire).
http://www.scpr.org/programs/madeleine- ... say-they-/