A unified command responding to the May oil spill off the California coast said more than 90 percent of the contaminated shorelines have met cleanup goals.

"Of the 96.5 miles of shoreline surveyed in Santa Barbara and Ventura counties, 91 percent have met cleanup goals," the unified command said in its latest operational update. "Clean areas will continue to be monitored for re-oiling which may occur, especially with the natural oil seeps in the area."

Line 901, a pipeline system operated by Plains All American leaked as much as 2,500 barrels of oil in Santa Barbara County in mid-May. About 500 barrels may have reached the waters off the coast of Refugio State Beach in a release the Environmental Protection Agency said was the worst spill in California in the last 25 years.

The federal Pipeline and Hazardous Materials Safety Administration said it found "extensive" corrosion on the breached pipeline, with walls degraded by as much as 74 percent of their original thickness in some locations.

Sheen has long since dissipated from the California coast and the volume of recovered oil-water mixture tied to the spill has not increased in the past week. The amount of oiled vegetation, sand and soil has seen minor increases since June 16.

In terms of wildlife, 190 dead birds have been recovered, up five from last week, and 103 mammals have been found dead, up 11 from June 16.

"Cleanup continues on other parts of the shoreline, especially cobble and rock areas which require hand crews, and in the excavation area in the vicinity of the initial release," the response team said.