Police believe a fire at a factory in Long Eaton may have been started deliberately.
Firefighters were called to the incident at Hydrogrow Systems Ltd in Farm Road at 10.40pm on Tuesday.
Crews tackled the blaze for an hour and 20 minutes before leaving the scene at just after 12am.
There were no reports of any injuries.
A spokesman for Derbyshire police said: “The fire was believed to have been started deliberately.
“We will carry out a joint investigation with the fire service.”
Anyone with information should call police on 101 or Crimestoppers on 080 555 111.