A British couple touring the grounds of the notorious Alcatraz prison in the United States claim that a photograph they took during the tour reveals the presence of a ghost.

Sheila Sillery-Walsh was touring the San Francisco, California jail alongside her partner Paul Rice in April when she used her iPhone to snap a photo through the window of one of the prison blocks.

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When she glanced down at the image in her phone, Walsh reportedly saw a female figure in the picture, but when she glanced back up at the room, there was no one inside.

"I knew straight away that the woman in the photo was a ghost and showed the snap to Paul," the UK native said. "From that point onwards, I wasn't interested in the Alcatraz tour anymore. I just kept looking at the picture over and over again!"

Alcatraz is a formal federal prison located on an island in San Francisco Bay. During its history as a prison, Alcatraz housed some of the most infamous criminals in American history, including Al Capone, Mickey Cohen, and George "Machine Gun" Kelly.

During its 29 years of operation, the penitentiary boasted that no prisoner had every successfully escaped, although many attempts were made.

Since its closing in 1963, Alcatraz has been transformed into a major tourist destination, especially for those interested in the paranormal.

The prison features night tours, and visitors have claimed to see apparitions numerous times in the past. However, authorities remain firm in saying that the former penitentiary has no ghosts.

"Spiritualists and people who want to believe in ghosts often claim to pick up haunted auras and ghostly feelings when visiting Alcatraz. However, there are no authenticated cases of ghost sightings by any of Alcatraz's residents over the years, whether they were soldiers, prisoners, correctional officers, family members or park rangers," reads the FAQ on the website of Alcatraz Cruises, which provides ferry service to the island.

TagsAlcatraz Ghost, Alcatraz tours, Alcatraz Cruises