New data shows the oily three-mile-long sheen that developed off the coast of Goleta last week was caused by natural seepage.
The U.S. Coast Guard says samples of the oil sent for cross testing at its lab in Connecticut over the weekend showed it was a match with other sampled seepage in the area.
The size of the oil sheen was cause for alarm for many following May's oil pipeline rupture along the Gaviota Coast.
The oil in this more recent case was too thin to be contained using traditional methods, so it was left to naturally dissipate.