California Governor Jerry Brown has declared a state of emergency in Santa Barbara County following a coastal oil pipeline spill.

The move on Wednesday night frees up emergency state funding and resources to help in the clean-up efforts

The oil spill has fouled beaches and threatened wildlife along a scenic stretch of the California coast spread across 14km of ocean as cleanup efforts began and federal regulators investigated how the pipeline leaked.

Workers in protective suits raked and shovelled stinking black sludge off the beaches, while boats towed booms into place to corral the two slicks off the Santa Barbara coast where a much larger spill in 1969, the largest in US waters at the time, is credited with giving rise to the US environmental movement.

Up to 400,000 litres spilled from an onshore pipe and a fifth of that, 80,000 litres, reached the sea, according to estimates provided by officials.

Crude was flowing through the pipe at 84,000 gallons an hour when the leak was first detected on Tuesday.

It took three hours to shut down, though company officials did not say how long it leaked before it was discovered or discuss the rate at which oil escaped.

Pipe investigated

Federal regulators from the Department of Transportation, which oversees oil pipeline safety, investigated the leak's cause, the pipe's condition and the potential regulatory violations.

The 60cm pipe, built in 1991, had no previous problems and was thoroughly inspected in 2012, according to Plains All American Pipeline, which owns the pipe.

The pipe underwent similar tests about two weeks ago, though the results had not yet been analysed.

"Plains is taking responsibility and paying for everything associated with this spill," said Darren Palmer, a district manager with the company.

There was no estimate on the cost of the cleanup or how long it might take.

A combination of soiled beaches and pungent stench of petroleum caused state parks officials to close Refugio State Beach and El Capitan State Beach, both popular campgrounds west of Santa Barbara, over the Memorial Day weekend.

Environmental damage was anticipated, but dead fish and oily birds had not been found in the calm seas or rocky coast by late morning, said Captain Mark Crossland of the state Department of Fish and Wildlife.

Source: Agencies