Fire crews were called to the Grade II-listed old Accrington Police Station, in Lancashire, just after midnight on July 21 after reports that people had been trapped inside.
Those trapped were taking part in a Most Haunted Experience ghost hunt, which gives the public a chance to go along with crew from the hit TV series on a ghostly expedition.
They may have gotten more of a fright than they bargained for when the cell door became locked and they were trapped for about two hours.
A Lancashire Fire Service spokesman said crews, including a team from urban search and rescue attempted “to gain entry with a saw” and the people were released shortly after three in the morning.
Ghost hunting crew manager, Jenny Bryant, said it was unclear how the door became locked as it had been set in a position to stop the doors from closing.
“There is lots of the stuff which cannot be explained and we can’t marry it all up,” she said.
“We are still investigating but we are looking to put wooden blocks in the lock so it won’t happen again.”
She said seven guests were on the ghost hunt, with former police officer Gareth Berry, Mary Beattie, Wendy Postma and then Gregg Smith from the show.
But Ms Bryant said once out of the cell the guests had told the team they were happy with how they had been cared for by the crew.
“The guests were looked after during the whole situation and we made sure they were safe and got some drink. They were all upbeat and everyone was fine,” she added.
“We don’t know if we can call it paranormal, but at the moment it is a mystery.”