A HUGE cannabis farm worth up to £1milllion has been discovered at a former mill.

Police said the drugs were found across the building's three floors on the corner of Wood Street and Hacking Street in Darwen.

Several police units, including crime scene investigation vans, an operations support unit, several unmarked cars and police dogs were called to the mill at around 9.40am today.

Eyewitnesses said they saw the police smashing their way into several metal shutters at the former mill.

One nearby resident said: "There was about 20 officers there at its peak, with many coming and going.

"I didn't know what was going on and it must have been something very serious to have so many police there.

"I could see police crowbarring their way into the shutters and ramming the doors in.

"We could see police officers on the roof at one point while there were dogs going in and out from both ends of the building.

"The police came here a few months ago, but it was not on this large scale."

A fire service spokesman said fire crews were called by the police to assist in gaining access but were told to stand down before they arrived.

Another Hacking Street resident said: "It was rather scary seeing all the police outside.

"There was so much commotion and noise coming from there it was quite intense.

"I haven't seen anything going on there really, it just looks horrible and run down.

"Quite frankly it needs pulling down and made into something nice."

Police remained on the scene for more than four hours.

Cllr Dave Smith, who represents the area on Blackburn with Darwen Council, said: "I am pleased all this stuff is now off the streets of Darwen, absolutely.

"I walk past there regularly and I have never seen anyone go in or out.

"The mill has been empty for a number of years apart from a small space used for storage."

A police spokesman said: "A warrant has today been executed at a mill on Wood Street, Darwen.

"In a concealed area inside the mill officers discovered an extensive cannabis farm, spanning across three floors, worth a potential value of up to £1million. Our enquiries are on-going."