

What could possibly cause rocks picked up at San Onofre State Beach to ignite in the pockets of a woman's cargo shorts? To scientists, the answer seems hard to come by.

A 44-year-old San Clemente woman, who has not been identified, went to the beach with her family on Saturday, where her children collected colored rocks.

Authorities said the woman told them she took the rocks from her children, put them in her pocket and that -- after the family returned home -- the stones ignited in her right pocket, authorities said.

Capt. Marc Stone of the Orange County Fire Authority said paramedics arrived to find that the woman had suffered second- and third-degree burns from her right thigh to her right knee, as well as second-degree burns on her right hand.

The woman remains hospitalized. Her husband also had burns on his hands after attempting to help her.

The Orange County Health Care Agency was called in to examine two of the rocks -- one of which was large and gray with orange streaks, and another an emerald color also flecked with orange. Tests revealed a "phosphorous substance" on the rocks, which have been sent to a state laboratory for further testing, said Tricia Landquist, an agency spokeswoman.

The situation, however, is puzzling to scientists who said that chemicals that would combust in that way aren't likely to be found on a beach.

Andrew Borovik, a professor of chemistry at UC Irvine, said phosphorus can remain stable under water and then can ignite once it touches the air.

But Borovik said he was unsure how the phosphorous substance could become part of a rock.

"I don't know if it exists just sitting around on the beach," Borovik said. "It just seems unlikely."