Workers scrambled to clean oil pollution along a series of California beaches near Los Angeles on Thursday, barely a week after a huge oil spill further up the coast.

An unknown tar-like substance began washing ashore from El Segundo Beach south to Redondo Beach on Wednesday, the Los Angeles County Department of Public Health said.

At a news conference, US Coast Guard spokeswoman Charlene Downey said "significant progress" was made overnight in the clean up.

"Our teams have worked ... on the ground and in the air and on the water, (and) have reported that there appears to be no new tar balls or anything additional to the amount that we have recovered thus far," she said.

"Our air crew did observe a sheen off the South Bay, which from what we understand is typical for that area.

"But what we believe to be pretty good news is that it doesn't appear to be any in the surf, the surf line, (like) we saw yesterday."

The seafront closedown also included Hermosa and Manhattan beaches. The stretch of coastline is regularly used by surfers, as well as locals and tourists.

Helicopter crews conducted flyovers in the area to try to determine where the substance has come from.

The unidentified pollution comes after thousands of gallons of oil spilled into the ocean, some from a ruptured pipe near Santa Barbara, some 100 miles (160 kilometers) northwest up the coast.

There was no immediate sign of a link between the two events.

Environmental group Heal the Bay said it was too soon to say if the material in the new pollution case could be linked to the oil spill near Santa Barbara.

"It is simply too early to tell where the oil comes from... from natural seepage or from an oil spill from a local refinery or a pipeline located nearby," said a spokesman.

In last week's Santa Barbara oil spill up to 105,000 gallons leaked from a crude pipeline. Two beaches were closed, and remain so until June 4, officials said Thursday. Fishing rights were also suspended within a 30-kilometer by 10-kilometer area.

About 10 seals and sea lions covered in oil were rescued, while dead animals included lobsters and pelicans.

Santa Barbara was the scene of what was then the largest oil spill in US history, when in 1969 several million gallons of crude spewed into the ocean after an oil rig blowout.