SAN CLEMENTE (AP) — Officials at Camp Pendleton are investigating how phosphorous got on two rocks that ignited a fire in the pocket of a woman’s shorts after she picked them up on San Onofre State Beach.

The Orange County Register reported that Capt. Barry Edwards declined to provide details of the investigation and doesn’t know how long it may take.

The beach is on military land and state parks officials say phosphorous is used by the military.

San Clemente resident Lyn Hiner visited the beach on May 12 and tucked some rocks into the pocket of her shorts, which later ignited, causing severe burns.

The stretch of beach between Cypress Shores of Trestles, where the rocks are believed to have been found, has been declared safe by San Diego County health officials.

» RELATED: Woman Severely Burned After Rocks Spontaneously Combust In Pocket

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