A UK woman touring the infamous Alcatraz prison in California claims she took a picture of one of the island's ghosts.

Sheila Sillery-Walsh, of Birmingham, England, was doing an audio tour of the facility in April when she stopped and used her iPhone to take a picture through the window of a visitation block, the Daily Mail reported Tuesday.

"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," she said according to the newspaper. 

"I knew straight away that the woman in the photo was a ghost," the 48-year-old teaching assistant said.

The ghost appears to be a woman looking sideways at the camera, dressed in black with her dark hair pulled back.

Sillery-Walsh showed the photo to her partner, Paul Rice, who at first thought it was just his companion's reflection.

"But with closer inspection, it's obvious that this is not the case at all," said Rice, who was with Sillery-Wash when the photo was taken, according to the Daily Mail. Rice said the woman appears to be dressed in clothing from the '30s or '40s.

"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."

Alcatraz, located on an island off the coast of San Francisco, was notorious for housing some of America's most dangerous criminals, including Al Capone and Mickey Cohen, from 1934 until 1963. It is now a tourist attraction operated by the National Park Service.

Throughout the years there have been several claims of ghost sightings at the island prison, coming from visitors as well as former prison guards, the Daily Mail reported.

But park officials maintain the island is not haunted.

"Spiritualists and people who want to believe in ghosts often claim to pick up haunted areas and ghostly feelings when visiting Alcatraz," reads a website for Alcatraz Cruises, according to The Huffington Post. "However, there are no authenticated cases of ghost sightings by any of Alcatraz's residents over the years."