Crop circle
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Mystery of new California crop circle

31 December 2013 Last updated at 09:13 GMT

California residents have been left puzzled by a mysterious crop circle which appeared at a farm over the weekend.

The pattern, in Salinas Valley, near Monterey, was reported by two friends in a YouTube post.

They claimed to have seen two bursts of light before dawn on Sunday.

No-one has claimed responsibility.

Update 7 January 2014: The technology firm Nvidia later said it had created the crop circle as a stunt.