Subscribe | UPI Odd Newsletter Subscribe SAN FRANCISCO, June 19 (UPI) -- A British tourist may have captured a lot more than a shot of the inmates' visitation waiting room when she snapped a photograph at Alcatraz. According to Sheila Sillery-Walsh, she photographed a ghost. Advertisement In the image, a woman appears to be looking directly through a window at the top of a door. "When I glanced at the photo on my mobile, I saw this dark female figure in the picture. I looked at the window again and there was no one in the room," Sillery-Walsh told the Daily Mail. "From that point onwards, I wasn't interested in the Alcatraz tour anymore. I just kept looking at the picture over and over again." Sillery-Walsh has been trying to identify the woman in the photo by contacting former Alcatraz staff members, but the effort has been unsuccessful thus far. "I am so curious to know who she could be though -- perhaps she was a female visitor of a prisoner who kept returning back," Sillery-Walsh said. "I would love to know why she's shown herself in my photo." Former Alcatraz prison guard George DeVincenzi told KPIX 5 that he thought the image in the photo was just shadows. "Personally I don't believe in ghosts," he said. Advertisement Read More Murkowski wary of Keystone XL oversell Gazprom starts clock on Chinese gas pipeline Tanzania rewarding for Statoil Australian hospital rejects 440-pound body from morgue for being 'too fat' #FacebookBack: Facebook up and running after 30-minute outage