More than 1,000 cannabis plants have been found in a former Debenhams building in Derbyshire.
Police discovered the farm on the upper floors of the building on Victoria Street in Derby city centre at around 6.30pm on Thursday (January 14).
Officers have been working closely with the owners of the building to discover how the set-up was established and who was involved.
Detective Inspector Darren De’Ath said: “The investigation is at an early stage and we have not yet made any arrests.
“We’re appealing for help from the public. This is a busy area of the city centre and it’s very likely that someone has seen suspicious activity in the area.
“I’d like to hear from anyone who has seen people carrying equipment, wood, metal drums or anything else unusual at any time during the last year.”
Anyone with information can contact Det Insp De’Ath on 101, quoting incident number 420/14/01/16.
Alternatively, call Crimestoppers anonymously on 0800 555 111.