GOLETA (CBS/AP) — The Coast Guard says a 2-mile-wide oil slick that mysteriously materialized off the Southern California coast is expected to dissipate on its own in the days ahead.

Petty Officer 1st Class Sondra-Kay Kneen (NEEN) says authorities still don’t know where the slick that surfaced in the Santa Barbara Channel came from.

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The oil-rich area is known for frequent natural seepage.

Two months ago, however, the area was flooded with 100,000 gallons of crude when a pipeline ruptured.

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Kneen says Wednesday’s slick isn’t thick enough to be scooped up and doesn’t appear to have reached shore anywhere

It was first observed about 12 miles from the area where the pipeline ruptured.

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