Just a week after a ruptured oil pipeline gushed 101,000 gallons of crude into the Pacific ocean off Santa Barbara, another California beach has been closed because of a mystery oil slime.

Gunky black goop spread across 6.5 miles of coastline, coated pelicans and sea lions and prompted the shut down of popular Manhattan Beach in Los Angeles. The source of the tar-like substance hasn't yet been identified, reports ABC News.

"We are continuing to analyse the beaches and try to determine the source of the tar balls and tar patties that washed up on shore yesterday," Charlene Downey of the US Coast Guard said at a press conference.

Wildlife experts were on the scene in a frantic bid to clean off water birds and sea mammals.

The clean up continues, meanwhile, north of Los Angeles at Refugio Beach where workers for the Plains All American oil company have only managed to clean up to a tenth of the crude that spilled unchecked for hours from one of its pipelines in Santa Barbara last week.

A permanent ban on drilling off the coast of Santa Barbara failed to pass the State Assembly last year, giving a major boost to drilling plans by Sunset Exploration and its partner Exxon Mobile. Environmentalists are now pleading with the legislature to reconsider, particularly in the wake of the recent devastating oil damage to the legendary California coast.