Photos of the white, strange-shaped object in a clear-blue sky have been sent to the Mutual UFO Network (MUFON) for examination.
An unnamed photographer snapped the images from their garden in Oceanside, California, on Monday.
In a report to US-based MUFON, which is the world's largest organisation dedicated to UFO research, the witness said: "It was a clear day and not a cloud in the sky.
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