Phosphorus may be to blame for rocks catching fire, burning woman

The leg of a woman's cargo pants caught fire last Saturday after being filled with rocks she'd collected from San Onofre State Beach. The woman remains hospitalized with third-degree burns to her leg as Orange County health officials hypothesize that phosphorus may have coated the rocks. Where the phosphorous may have come from, however, remains a mystery.

The woman's children had picked up the rocks on San Onofre State Beach in San Diego County, near the Camp Pendleton Marine base. A base spokesman said there’s no evidence that any material used at Pendleton ended up on the rocks. But, he added, the base is cooperating with local officials investigating the incident.

White phosphorus is used in incendiary bombs, smoke bombs and tracer ammunition. The chemical is also used to make flares and safety matches.

Phosphorus flares are used as markers in military exercises, and by divers to light the dark ocean waters. Federal safety rules also require recreational boaters to carry flares.

“The field evaluation of the rocks indicated they may have been coated or contained some phosphorous material," said Denise Fennessey, who is with the Orange County Environmental Health Department, which checked out the rocks. "Right now they’re at a state-certified lab to verify those field tests.”

She said the results are expected in two weeks.

The rocks were wet, but later dried in the woman’s pants pocket, causing her burns. Fennessey said the flammable chemical could have ignited when exposed to air.

Military phosphorus finding itself on the beach is not unheard of. Earlier this year a non-dangerous phosphorus flare, used often in military exercises, washed ashore in Palm Beach, Florida.