Four men have been arrested after police say they discovered a "subterranean cannabis factory".
The raid at a factory near Tenbury Wells in Worcestershire was carried out last Friday (July 13) following a joint operation run by West Mercia, Gloucestershire and Gwent police forces.
They found more than 200 plants, with a street value of £100,000.
Those arrested were a 32-year-old man from Herefordshire; a 58-year-old man from Gwent and men aged 35 and 22 from Gloucester, who were all held on suspicion of conspiracy to produce cannabis.
All four have been bailed until September pending further inquiries.