A British tourist snapping photos on Alcatraz claims to have captured the image of a ghost, complete with hair and clothing from a bygone era.

"I knew straight away that the woman in the photo was a ghost," Sheila Sillery-Walsh, 48, 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, a teaching assistant from the UK, took the image with her iPhone. She quickly showed it to her partner, Paul Rice.

"I have no logical explanation for the girl in the picture -- I'm baffled by her! It's funny because she's staring right at the camera, with a knowing look," Rice told the newspaper. "I was really skeptical about ghosts before but I'm a bit more of a believer now. I do think that the woman in the photo is a ghost."

Alcatraz, an island in San Francisco Bay, was a notorious federal prison from 1934 until 1963. Today, it's part of the Golden Gate National Recreation Area and managed by the National Park Service.

Alcatraz is a popular tourist destination in San Francisco, especially for fans of the paranormal. The park is open for night tours, and was even featured in an episode of the SyFy television show, "Ghost Hunters."

Park officials, however, say there are no ghosts on the island.