The sheriff's office says 35-year-old Danielle Staley was last seen at a bonfire on Nov. 6, around 11 p.m., near Rio Del Mar State Beach in Aptos, California.
Her belongings were found on the beach.
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Detectives say new information suggests she may be at risk and foul play may be involved. They say she was last wearing a dark hoodie sweatshirt and leopard-print leggings.
Investigators are asking anyone in the area with surveillance video to review their footage from Nov. 5-7 for possible sightings or clues.