Police in Britain say a building they were watching had people coming and going at all hours, numerous wiring and ventilation ducts visible, and was emitting a lot of heat—all "classic cannabis factory signs." But when West Midlands police raided the factory in an industrial area last week, they uncovered a Bitcoin mining operation that was using stolen electricity, the Guardian reports. In a Facebook post, police said the operation was running around 100 computers to mine for Bitcoin, an energy-intensive process that involves solving complex equations to unlock blocks of the cryptocurrency.
"It’s certainly not what we were expecting,” police Sgt. Jennifer Griffin said in a statement, per CNBC. "It had all the hallmarks of a cannabis cultivation set-up and I believe it’s only the second such crypto mine we’ve encountered in the West Midlands." She said that her understanding is that cryptocurrency mining itself isn't illegal—but stealing electricity from the grid clearly is. Police say the equipment was seized and while no arrests have been made yet, they have a lot of questions to ask the unit's owner. (Read more bitcoin stories.)