Neighbourhood officers were making enquiries in the area when they noticed a "strong smell" emanating from a warehouse in Commercial Street on August 26, 2020.
Numerous boxes filled with pre-packaged bags of cannabis resin and cannabis bush were discovered once police entered the building - valued in the region of £3.5 million.
This morning (June 29), officers executed warrants at addresses in Granville Street and Marles Court in Burnley, Higher Reedley Road in Nelson, and Revidge Road in Blackburn.
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Four men were subsequently arrested on suspicion of conspiracy to supply cannabis.
Det Chief Insp Tim Brown, from East Division, said: "This is a complex investigation looking into the large-scale importation of drugs from Europe into East Lancashire.
"Although we have made four arrests today our enquiries are very much ongoing.
"If anyone has information which could assist our investigation, I would ask them to make contact with the police as soon as possible."
The four men who were arrested are:
- A 35-year-old man from Nelson
- A 36-year-old man from Burnley
- A 33-year-old man from Blackburn
- A 59-year-old man from Burnley.
They are all currently in custody for questioning.
Mobile phones, suspected Class A drugs and a quantity of cash were also seized during this morning's raids.
Anyone with information should call police on 101, quoting log number 0994 of August 26, 2020.
Alternatively, independent charity Crimestoppers can be contacted anonymously on 0800 555111 or online at crimestoppers-uk.org.
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