Pyramid Lake, which had been closed to swimmers due to an algae bloom, will reopen on Saturday, officials announced.
Lab tests conducted earlier this week revealed the toxin levels merit a caution advisory but are safe for swimmers and boaters.
Users "should remain cautious of potential blooms," according to the state Department of Water Resources.
"Vaquero Swim Beach has been closed to swimming due to a higher concentration of algae toxins detected using a field test kit," according to a department statement.
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"Based on the latest laboratory test results, the advisory for the ... beach has changed from 'Warning' to 'Caution.' Emigrant Landing Swim Beach is also at 'Caution' level. Swimming is now allowed throughout Pyramid Lake, but recreational users are urged to avoid direct contact with blue-green algae, which can pose health risks, particularly to children and pets."
Officials had closed the lake to swimmers about three weeks ago.
Parents who were unaware of the warning said the algae sickened their 15-month-old child after when they took him for a dip in the lake near Castaic, according to news reports.