A small army of clean-up workers toiled Friday to scoop up crude oil deposits from a picturesque California beach, three days after a pipeline rupture unleashed thousands of gallons into the ocean.

The scenic Refugio State Beach and its neighbor El Capitan would usually be swarming with tourists over America's Memorial Day weekend, but were closed until further notice following Tuesday's spill.

Plastic bags filled with blackened sand piled up, and the stench of oil could be smelled from miles around. Workers had made significant progress on the beach but rocks remained coated in oil.

"The beaches are starting to look a lot better than they did a couple of days ago, but still it will be a long process," said David Mosley, a Coastguard spokesman.

"Something like that, it can take days or weeks to get back to pre-spill."

Some 300 clean-up workers have been mobilized and new teams are still arriving. Their ranks are boosted by many volunteers, but these need equipment and to undergo a brief training session before they can get to work.

Clean-up operations also aim to pump slicked oil from the ocean. About 105,000 gallons (40,000 liters) are estimated to have spilled.

Only a portion of this made it to the sea, but this was enough to form an oil slick about nine miles (14 kilometers) long.

Workers were also cleaning the hill overlooking Refugio beach, the site of the rupture. The leak affected a pipeline operated by Plains All America Pipeline.

Patrick Hodgins, a senior director with the company, said it could take months to find out what happened to the two-foot (60 centimeter) wide pipeline which dates back to 1987.

- Cause still unknown -

Plains came under fire Friday when local media including the Los Angeles Times reported that it had 175 safety and maintenance infractions since 2006 -- more than three times the national average.

During a press conference in Santa Barbara, Hodgins said that of these incidents, 20 were of leaks of less than one barrel of oil and many more less than five barrels.

The health impacts of the spill are still unknown. People have varying levels of sensitivity to the smell, Mosley noted, and some would get skin irritation or headaches.

Authorities are monitoring closely how the spill will impact the area's rich wildlife, which includes populations of sea lions, pelicans, dolphins and whales.

Until now, the only animals to have been rescued are five pelicans, a young sea lion, a dolphin and two other marine mammals.

Kyra Mills-Parker, deputy director of the network that rescues wild animals, noted the spill would have adverse impacts on wildlife that would be hard to document.

Since the spill, lobsters, pelicans and other animals coated in oil were found along beaches.

Fishing is prohibited until further notice in the area, even though authorities had not been immediately able to assess the spill's potential impact on the food chain.

The cost to the local economy is also unknown. A spokeswoman from the Santa Barbara tourist office said there had not been any significant cancelations in the area's hotels.

In the heart of this upscale ocean town about 100 miles northwest of Los Angeles, vacationers said they were not intending to swim. But not because of the spill.

"The water is too cold for us," a German student said.