Researchers believe the tar balls that closed a four mile span of shore today in Long Beach are not from natural oil seeps.
Rather, it's looking increasingly likely that they are related to the recent oil spill in Santa Barbara County, though there is no conclusive evidence yet.
Similar oily clumps washed up in large numbers over the last few days around Malibu, Manhattan Beach and other stretches of local coastline.
Tar balls form when crude oil mixes with seawater.
They do appear naturally around L.A. but usually only in very small numbers, according to Sarah Sikich, vice president for the environmental group Heal The Bay.
In such a scenario, the tar balls are created when oil trapped under the ocean floor creeps its way up through cracks in the earth and seeps out into the ocean.
"Earthquakes can affect the amount of natural seep flowing, plate tectonics movements can effect it," she noted.
Still, researcher David Valentine with UC Santa Barbara says the natural seeps around Los Angeles typically don't leak as much oil as do the ones around Santa Barbara County.
"They are not known to be really prolific," he explained.
On average, these seeps release about 10 barrels of oil a day into the Santa Monica Bay, according to Heal the Bay.
Still, this amount of oil doesn't produce hundreds of tar balls, like the sort washing up lately.
Valentine is testing the tar to see if it comes from the oil spill two weeks ago in Santa Barbara County.
Oil that comes up in a natural seep has a different chemical make up than oil pumped directly from the ground, since microbes change it as it moves through the earth.
Valentine expects the results from his testing to be ready in the next few days.
He added that prevailing winds and ocean currents could easily have carried remnants of the spill this far south.
In the mean time, Sikich with Heal the Bay is recommending that beach goers avoid the tarred areas since the tar can be hazardous to humans.