SOUTH LOS ANGELES ( —An explosion in an underground electrical vault last week in the South Los Angeles neighborhood of Hyde Park may have been caused by high levels of methane in the soil.

The Los Angeles Department of Water and Power reported Friday that the Sept. 6 explosion in the 6200 block of Brynhurt Avenue was not linked to a mechanical or electric failure in any equipment or cables.

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Instead, LADWP industrial hygienists discovered high levels of subsurface natural gas while inspecting the power system and electrical substructures in the area surrounding the explosion.

They notified the Southern California Gas Company, who on Sept. 9 found “elevated levels” of methane in the soil on Brynhurst Avenue, two blocks from the site of the explosion.

SoCalGas began work Tuesday on replacing a 150-foot section of a four-inch gas line. It has also been conducting pressure tests on the gas line under the supervision of the California Public Utilities Commission.

LADWP noted that its “high-voltage electric cables were not damaged and continued to supply power to the grid before, during and after the explosion.”

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The blast happened around 3:30 p.m., sending asphalt and two 250-pound manhole covers flying.

Brian Jefferson and his brother Adrian, who live nearby, described the scene to CBS2.

“I just heard a real loud sound, kind of like a boom, like there was truck accident,” Brian said.

No one was hurt in the blast, but several parked cars were damaged and windshields were shattered.

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“I heard this big old explosion like consecutively four times in a row, and I was like ‘Whoa, what was that?’” Adrian added.