A demolition crew in Middletown, Pennsylvania uncovered a secret underground room after they tore down a building in May.

WPMT reports historians have new details from the deed.

Construction halted when the walled-off entrance was found.

“After we dug that out, we were just standing around talking, and the whole side fell down,” said worker James Thornton. “That’s when we noticed the hole.”

Theories abound about whether the room was used in the Underground Railroad, or during Prohibition. Historians say evidence so far points to the latter.

The Middletown Area Historical Society is consulting with the Pennsylvania Historic Museum Commission. They say the large room with vaulted ceilings has architecture consistent with a cold storage, used to keep drinks and food.

The deed shows the demolished building went up between 1870-1880.

“On the deed, it doesn’t say, D for dwelling, it says SAL which he is thinking means saloon possibly,” says historian Robin Pellegrini. “So there could’ve been a speakeasy in there.”

She says more investigation is needed to see if there is a tunnel connected to the room, if it was used for anything else, or as part of the Underground Railroad.

“I’m hoping they get a chance to knock that back wall down,” says Thornton. “If anything, it’s behind those walls.”