A CANNABIS farm has been uncovered in the open air yards from a family picnic site off a major road.

Police said they were amazed to find 50 plants between 5ft and 8ft tall down a ravine.

The cannabis was among the tallest ever seen by local officers.

There has been a number of farms discovered in houses and derelict buildings in East Lancashire over the last 12 months but police said it was rare to find and outdoor cannabis farm.

A member of the public made the discovery down a ravine off the Grane Road, linking Blackburn and Haslingden, near to the Clough Head picnic site.

The drugs - which typically needs warm temperatures to prosper - were in grow bags and plant pots with fertiser nearby.

Police suspect they had been grown inside before being placed in the isolated spot to grow further.

Officers said it was highly unusual for drugs gangs to set up outdoor cannabis farms in the UK due to our cooler climate.

A hunt has been launched for the people behind the firm and detectives are urging anyone with information to contact them.

Detective Sergeant Nicky Bithell said: “Cannabis growing outdoors is something that I have never come across before even when I worked on the drug squad.

“It is usually found in a confined, secure space.

“The plants are usually grown for personal monetary gain, so by putting them outdoors, someone has taken a substantial security risk.

“There is a lot of danger to the local community because if kids had found them the consequences could have been fatal eventually.”

Cultivating cannabis indoors usually involves special lamps, a hydroponics system and nutrients being supplied to the plants at regular intervals.

Detective Constable Mick Smith said a woman had made the discovery when she was out walking.

He added: “Officers discovered about 50 mature cannabis plants down a small ravine near Clough Head picnic site.

“They must have been there for quite some time as they were between 5ft and 8ft tall and were certainly the biggest anyone had ever seen before.

“It looked as though they had been intended for cultivation as they were in grow bags and plant pots with fertilizer and pot holes close by.”

Officers said the plants have been removed from the site and will be destroyed.

Anyone with information should contact Ratwenstall CID on 01706 237444 or Crimestoppers on 0800 555 111.