Two months after a pipeline spill, oil sheen appearing off the California coast is consistent with what would be expected from natural seeps, a geochemist said.

Authorities from Santa Barbara confirmed oil sheen about 1,000 feet from the shore of Goleta Beach. Responders said the sheen was about 3 miles long and is too thin to clean, meaning it will be allowed to dissipate naturally.

While the county public health department said there is no immediate threat from the offshore oil, residents are advised to avoid contact with areas where oil may be present.

"All county beach parks remain fully open for visitors," the county said in a statement. "This includes both swimming and pier fishing at Goleta Beach."

Reports of sheen come more than two months after Plains All American reported a release from a pipeline system in Santa Barbara County. The release spilled about 2,500 barrels of oil, which migrated more than 100 miles along the California coast.

Several area beaches were closed and mammalian and bird deaths were associated with the May spill on the county's Refugio Beach.

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.

David Valentine, professor of microbial geochemistry at the University of California, Santa Barbara, said in response to email questions the appearance of sheen was likely the result of natural oil seeps and not residual contamination from the Refugio Beach spill.

"We won't have any chemical data for some time, but the reports I received from the team [on site] are that the distribution, density and consistency were well within the normal bounds of what we observe from natural seeps," he said. "From everything I can discern, the appearance of oil on Goleta Beach today is well within the normal range observed at this location."

Sheen form the Refugio Beach incident had dissipated by late June.