Lifeguards closed a stretch of Santa Monica beach on Wednesday after a previously-unknown substance in the water was discovered.
Los Angeles County firefighters said the thick white substance was identified as linoleic acid, a non-toxic substance often found in plant foods like nuts and vegetable oils.
It was still unknown where the acid originated and how it got into the water.
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When the substance washed ashore Wednesday, lifeguards closed down a stretch of the beach for several hours. Swimmers were asked to stay clear of the water.
Cleaning cleaned up the site Wednesday and reopened the beach on Thursday.