The Post was alerted to a police raid ongoing at a building in Manchester Road, off Church Street, at around 9.15am.
When we arrived at the scene, officers were executing a drug warrant and had cut a hole through a side entrance to flats above the Shisha Cafe Lounge.
The Post was invited inside where hundreds of cannabis plants were found growing under blazing lights over its three floors.
No one has been arrested but officers said it looked like someone might have fled from the building via the roof before the raid.
Police said they were made aware of the cannabis farm after receiving a tip-off from a member of the public.
The plants have been seized for destruction and the equipment - including high-powered lights and fans - is being dismantled.
Preston Task Force said enquiries are already under way to find those responsible for the cannabis farm.
You can watch our footage of the raid in the video player above.
An officer at the scene told the Post: "It's a joint operation between Preston Task Force and Preston Neighbourhood Team.
"Acting upon community intelligence, a drugs warrant has been executed at this location.
"A substantial amount of cannabis has been found and we're currently in the process of recovering it."