Theresa Robinson, 76, was last seen around noon on Thursday, Dec. 19, near Innovation Drive in York, according to West Manchester Township police.
Robinson is described as a white female, five-foot-one, 100 pounds, with green eyes, gray hair, and glasses.
She may be driving a black 2005 Mercury Montego bearing Pennsylvania registration KLY2954, police said.
Authorities believe Robinson could be at special risk of harm or injury.
Anyone with information on Robinson's whereabouts is urged to contact police immediately by calling 911 or the West Manchester Township Police Department at 717-854-5571.
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