Firefighters responding to a sounding smoke alarm stumbled on a cannabis factory last night, police said.
Officers were called to a flat above a shop in Harrowside, South Shore, at around 9pm, a spokeswoman for Lancashire Police said.
"Smoke alarms were going off in the property and firefighters were struggling to gain entry, so they asked us to attend," she added.
"We gained entry and found cannabis inside. We are still at the scene."