Officials reopened South Bay beaches Friday evening after crews spent two days clearing the sand of tar balls that washed on shore, U.S. Coast Guard and Los Angeles County Department of Health officials said.
The closure, which affected nearly all South Bay beaches, from El Segundo to the Torrance-Redondo Beach border, had forced officials to shut down the portion of sand from the lifeguard towers to the water.
County officials advised beachgoers to stay away from cleanup efforts and out of the water because contact with the tar balls could result in skin irritation.
Most of the tar pieces were found in the Redondo Beach Jetty, King Harbor Jetty and Hermosa Beach, said Coast Guard Commander Charlene Downey. Earlier Friday, crews have retrieved 40 cubic yards of tar balls, equal to three dump trucks.
The origin and chemical makeup of the tar balls still remain a mystery.
Officials gathered samples of the tar for testing. Test results could take a few days to several weeks.
The substance, however, has tested positive for low amounts of volatile organic compound, making it slightly flammable.
Scientists with the National Oceanic and Atmospheric Administration are investigating whether the tar balls traveled from Santa Barbara County, where last week's oil spill released as much as 101,000 gallons of crude. An estimated 21,000 gallons of oil spewed into the Pacific.
The tar balls could have come from natural seepage, which is not uncommon in the area.
"Anything is possible," Downey said. "It's a dynamic environment."
The baseball- to football-sized tar balls were first spotted about 10 a.m. Wednesday just off the coast, and within hours they had washed ashore and coated sand between 34th Street in Manhattan Beach and Longfellow Avenue in Hermosa Beach.
On Thursday night, an oiled loon was found by a good Samaritan who tried to wash the gunk off but was unable to do so. A rescue team is caring for the bird. No other wildlife has been affected by the tar substance, said Saul Garcia of the California Department of Fish and Wildlife.