Police discovered 1,000 cannabis plants in a disused factory after being called by the fire service who were dealing with a fire at the building.
Two fire crews from Leicester's central fire station went to the disused two-storey factory in Brazil Street, off Aylestone Road in the city shortly after 5.30am after receiving reports that a door into the building was on fire.
Once inside they found several seats of fire - thought to have been caused by hydroponic lighting used to grow the plants having short circuited.
The firefighters called for reinforcements from the city's western fire station and tackled the fires wearing breathing equipment.The fires were put out by 7am.
A Leicestershire Police spokeswoman said: "Police were called by the fire service at 5.40am. The road was closed but no evacuation was necessary as the buildings in the area are commercial.
"Once inside officers discovered 1,000 cannabis plants which have been taken away and will be destroyed. No arrests have been made. It is a large, empty factory. We are trying to make contact with the owner who is abroad. It's believed electrics used to grow the plants had blown."
