MARTINEZ (CBS SF) — The source of a mysterious rumbling in the Concord-Clayton area that had been keeping residents awake at night has been confirmed.

The rumbling had residents searching the skies for spaceships with sounds like a gigantic washing machine, one resident said.

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The noise was so loud it caused neighborhood dogs to bark so loud that resident Krage Assanee couldn’t hear the noise causing it.

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Nobody knew for sure what the sounds were until KPIX heard from the Tesoro refinery in Martinez.

They said the refinery is undergoing planned maintenance which resulted in flaring and noise.

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