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.
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.
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Cleaning cleaned up the site Wednesday and reopened the beach on Thursday.