Phosphorous May Have Been on Burning Beach Rocks Southern California authorities say phosphorous may have coated beach rocks that caused a woman's shorts to catch fire, leaving her with severe burns. Denise Fennessey of the Orange County environmental health division says Thursday that field tests indicated that the substance coating two rocks was phosphorous but they'll be sent to a state lab for verification. She also says the flammable chemical could have ignited when exposed to air. Authorities say the 43-year-old woman's cargo pants caught fire on Saturday and she was hospitalized with third-degree burns to her leg. She remains hospitalized Thursday. The woman's children had picked up the rocks on San Onofre State Beach in San Diego County, which is near the Camp Pendleton Marine base. A spokesman says the base is working with authorities to determine whether any military material might have contaminated the area.